RRB Group D · Topic Collection

Quantitative Aptitude PYQs

Arithmetic, number systems, percentages, ratios, profit and loss, time and work, algebra, geometry, mensuration, and trigonometry.

4310 Total Questions161 Official PapersYears: 2018–2026Search in Quantitative Aptitude
Showing questions 861–880 of 4310Page 44 of 100
RRB Group D Official Paper (Held On: 27 Dec, 2025 Shift 1) (Previous Year Paper)·Mathematics
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Question 861

RRB Group D 2025• Mathematics• Mathematics

The sum of the present ages of two sisters is 67 years. Five years ago from now, the elder sister was twice as old as the younger one. Find the elder sister's current age.

  1. AOption (a)

    27 years

  2. BOption (b)

    43 years

  3. COption (c)

    40 years

  4. DOption (d)

    24 years

View answer & explanation

Correct answer

Answer: (b)B.

43 years

Why this answer is correct

Shortcut Trick

Sum of ages 5 years ago → 67 − (5 × 2) = 57 years.

Age ratio 5 years ago (Elder : Younger) = 2 :

  1. Elder sister's age 5 years ago = (2/3) × 57 = 38 years.

Current age of elder sister = 38 + 5 = 43 years.

∴ The correct answer is 43 years.

Alternate Method

Given: Sum of present ages = 67 years. Ratio 5 years ago = 2 :

  1. Formula: Age after 'n' years = Age 'n' years ago + (n × 2 for two people).

⇒ Let ages 5 years ago be 2x and x.

⇒ Present ages = (2x + 5) and (x + 5).

⇒ (2x + 5) + (x + 5) = 67

⇒ 3x + 10 = 67

⇒ 3x = 57 ⇒ x = 19.

⇒ Elder sister's current age = 2x + 5 = (2 × 19) + 5 = 38 + 5 = 43.

∴ The correct answer is 43 years.

Additional Information

Age Difference Constant

The difference between the ages of two people always remains constant, regardless of the number of years passed.

Sum of Ages Change

If there are 'n' people, the sum of their ages increases or decreases by (n × number of years).

Ratio Method

When a constant number of years is added to both parts of a ratio, the difference between ratio units should be balanced if the age difference is known.

RRB Group D Official Paper (Held On: 27 Dec, 2025 Shift 1) (Previous Year Paper)·Mathematics
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Question 862

RRB Group D 2025• Mathematics• Mathematics

\( \text{If } \sec \theta = \frac{17}{12}, \text{ then what is the value of } \sin \theta? (0^\circ < \theta < 90^\circ) \)

  1. AOption (a)

    \( \frac{13}{17} \)

  2. BOption (b)

    \( \frac{12}{17} \)

  3. COption (c)

    \( \frac{\sqrt{145}}{17} \)

  4. DOption (d)

    \( \frac{\sqrt{170}}{17} \)

View answer & explanation

Correct answer

Answer: (c)C.

\( \frac{\sqrt{145}}{17} \)

Why this answer is correct

Shortcut Trick

Given sec θ = Hypotenuse / Base = 17 / 12.

Using Pythagoras Theorem: Perpendicular2 = Hypotenuse2 − Base2.

P2 = 172 − 122 = 289 − 144 = 145 ⇒ P = √145.

sin θ = Perpendicular / Hypotenuse = √145 / 17.

∴ The correct answer is √145/17.

Alternate Method

Given: sec θ = 17/12

Formula Used: sin2θ + cos2θ = 1 OR sec θ = 1 / cos θ

⇒ cos θ = 1 / sec θ = 12 / 17

⇒ sin2θ = 1 − cos2θ

⇒ sin2θ = 1 − (12/17)2

⇒ sin2θ = 1 − 144 / 289

⇒ sin2θ = (289 − 144) / 289 = 145 / 289

⇒ sin θ = √(145 / 289) = √145 / 17

∴ The correct answer is √145/17.

Additional Information

Trigonometric Identities

Fundamental relations include sin2θ + cos2θ = 1, 1 + tan2θ = sec2θ, and 1 + cot2θ = cosec2θ.

Right Angled Triangle Ratios

In a right triangle: sin θ = P/H, cos θ = B/H, tan θ = P/B, where P is perpendicular, B is base, and H is hypotenuse.

Pythagoras Theorem

For any right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides: H2 = P2 + B2.

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Question 863

RRB Group D 2025• Mathematics• Mathematics

A man walks 430 m in 10 minutes, 470 m in 11 minutes and 620 m in 17 minutes. Then, his average speed (in m/minutes) for the whole journey is:

  1. AOption (a)

    55

  2. BOption (b)

    44

  3. COption (c)

    40

  4. DOption (d)

    78

View answer & explanation

Correct answer

Answer: (c)C.

40

Why this answer is correct

Shortcut Trick

Average Speed = Total Distance ÷ Total Time

Total Distance = 430 + 470 + 620 = 1520 m

Total Time = 10 + 11 + 17 = 38 minutes

Average Speed = 1520 ÷ 38 = 40 m/minutes

∴ The correct answer is 40 m/minutes.

Alternate Method

Given:

Distance 1 (d1) = 430 m, Time 1 (t1) = 10 minutes

Distance 2 (d2) = 470 m, Time 2 (t2) = 11 minutes

Distance 3 (d3) = 620 m, Time 3 (t3) = 17 minutes

Formula Used:

Average Speed = (d1 + d2 + d3) ÷ (t1 + t2 + t3)

Calculations:

⇒ Total Distance = 430 + 470 + 620 = 1520 m

⇒ Total Time = 10 + 11 + 17 = 38 minutes

⇒ Average Speed = 1520 ÷ 38

⇒ Average Speed = 40 m/minutes

∴ The correct answer is 40 m/minutes.

Additional Information

Average Speed for Equal Distances

If a person covers two equal distances at speeds x and y, the average speed is given by (2xy) ÷ (x + y).

Relative Speed

Speed of two bodies moving in the same direction is (u − v) and in opposite directions is (u + v).

Unit Conversion

To convert kmph to m/s, multiply by 5/18. To convert m/s to kmph, multiply by 18/5.

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Question 864

RRB Group D 2025• Mathematics• Mathematics

For 6 innings, a cricketer had an average of 90 runs. In the 7th inning, he scored 157 runs. His average score increased by _______. (Round off the answer to the nearest whole number.)

  1. AOption (a)

    19

  2. BOption (b)

    20

  3. COption (c)

    10

  4. DOption (d)

    8

View answer & explanation

Correct answer

Answer: (c)C.

10

Why this answer is correct

Shortcut Trick

Deviation = New Score − Old Average = 157 − 90 = 67 runs.

Increase in Average = Deviation ÷ Total Innings = 67 ÷ 7 ≈ 9.57 runs.

Rounding 9.57 to the nearest whole number gives 10 runs.

∴ The correct answer is 10 runs.

Alternate Method

Given:

Average for 6 innings = 90 runs

Runs in 7th inning = 157 runs

Formula Used:

Average = Total Runs ÷ Number of Innings

Calculations:

⇒ Total runs in 6 innings = 6 × 90 = 540 runs

⇒ Total runs in 7 innings = 540 + 157 = 697 runs

⇒ New average = 697 ÷ 7 = 99.5714... runs

⇒ Increase in average = 99.57... − 90 = 9.57... runs

⇒ Rounding 9.57 to the nearest whole number ≈ 10

∴ The correct answer is 10 runs.

Additional Information

Average Change Formula

When a new value is added, New Average = Old Average + (Extra Runs ÷ New Total Innings).

Weighted Average

Weighted Avg = (n1 × A1 + n2 × A2) ÷ (n1 + n2), where n is the number of items and A is the average.

Batting Average in Cricket

Batting Average = (Total Runs Scored) ÷ (Number of times Out). In simple problems, innings played is often treated as times out.

RRB Group D Official Paper (Held On: 27 Dec, 2025 Shift 1) (Previous Year Paper)·Mathematics
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Question 865

RRB Group D 2025• Mathematics• Mathematics

The sum of two numbers is 88 and their L.C.M. is 870. The two numbers are:

  1. AOption (a)

    30, 58

  2. BOption (b)

    28, 60

  3. COption (c)

    23, 65

  4. DOption (d)

    35, 53

View answer & explanation

Correct answer

Answer: (a)A.

30, 58

Why this answer is correct

Shortcut Trick

Check options for Sum = 88 and LCM = 870.

Option (1): 30 + 58 = 88. LCM of 30 and 58: 30 = 2 × 3 × 5; 58 = 2 × 29. LCM = 2 × 3 × 5 × 29 = 870.

Option (2): 28 + 60 = 88. LCM ends in 0 but 28 is not a factor of 870.

Option (3): 23 + 65 = 88. 23 is prime, 870 is not divisible by 23.

∴ The correct answer is 30, 58.

Alternate Method

Given: Sum of numbers (x + y) = 88, LCM(x, y) = 870.

Formula: Product of two numbers = HCF × LCM.

⇒ Let the numbers be x and y.

⇒ x + y = 88

⇒ LCM(x, y) = 870

⇒ Prime factors of 870 = 2 × 3 × 5 × 29

⇒ Since sum is 88, one number must be 2 × 29 = 58 (as 29 is a large prime factor).

⇒ If one number is 58, then the other number = 88 − 58 = 30.

⇒ Verification: LCM(30, 58) = LCM(2 × 3 × 5, 2 × 29) = 2 × 3 × 5 × 29 = 870.

∴ The correct answer is 30, 58.

Additional Information

Product Rule

For any two numbers a and b, a × b = HCF(a, b) × LCM(a, b).

HCF of Sum and LCM

The HCF of two numbers also divides their sum and their LCM.

Prime Factorization Method

LCM is the product of the highest powers of all prime factors involved in the numbers.

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Question 866

RRB Group D 2025• Mathematics• Mathematics

\( \text{Find the value of } x \text{ if } 8(x)^\frac{1}{2} = \sqrt{6889} + \sqrt{4761} \)

  1. AOption (a)

    729

  2. BOption (b)

    361

  3. COption (c)

    529

  4. DOption (d)

    289

View answer & explanation

Correct answer

Answer: (b)B.

361

Why this answer is correct

Shortcut Trick

Identify square roots by looking at unit digits and nearest tens.

√6889 → ends in 9 (3 or 7), between 802 and 902 → 83.

√4761 → ends in 1 (1 or 9), between 602 and 702 → 69.

8√x = 83 + 69 = 152 ⇒ √x = 19 ⇒ x = 361.

∴ The correct answer is 361.

Alternate Method

Given: 8(x)1/2 = √6889 + √4761

Step 1: Calculate √6889

⇒ 802 = 6400 and 902 = 8100. Since 6889 ends in 9, the square root must be 83 or 87.

⇒ 852 = 7225. Since 6889 < 7225, √6889 = 83.

Step 2: Calculate √4761

⇒ 602 = 3600 and 702 = 4900. Since 4761 ends in 1, the square root must be 61 or 69.

⇒ 652 = 4225. Since 4761 > 4225, √4761 = 69.

Step 3: Substitute values back into the equation

⇒ 8√x = 83 + 69

⇒ 8√x = 152

⇒ √x = 152 ÷ 8

⇒ √x = 19

Step 4: Squaring both sides to find x

⇒ x = 192

⇒ x = 361

∴ The correct answer is 361.

Additional Information

Square Root Extraction

For a perfect square ending in 9, the unit digit of the root is 3 or 7; for 1, it is 1 or 9.

Squaring trick for 5

A number (n5)2 can be calculated as [n × (n+1)] followed by 25. e.g., 652 = (6×7)25 = 4225.

BODMAS Rule

Always solve operations in the order: Brackets, Orders (powers/roots), Division, Multiplication, Addition, Subtraction.

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Question 867

RRB Group D 2025• Mathematics• Mathematics

A tank can be filled by Pipe A in 9 hours and by Pipe B in 12 hours. Pipe C can empty the tank in 18 hours.

All three pipes are opened simultaneously, but Pipe C is closed after 4 hours. How much total time in all will it take to fill the tank completely?

  1. AOption (a)

    \( \frac{100}{11} \) hours

  2. BOption (b)

    \( \frac{42}{5} \) hours

  3. COption (c)

    \( \frac{22}{3} \) hours

  4. DOption (d)

    \( \frac{44}{7} \) hours

View answer & explanation

Correct answer

Answer: (d)D.

\( \frac{44}{7} \) hours

Why this answer is correct

Shortcut Trick

Let Total Capacity be LCM(9, 12, 18) = 36 units.

Efficiencies: A = 4, B = 3, C = −2. Combined efficiency (A+B−C) = 4 + 3 − 2 = 5.

Work in first 4 hours = 5 × 4 = 20 units. Remaining work = 36 − 20 = 16 units.

Time for A+B to finish = 16 ÷ 7 hours. Total time = 4 + 16/7 = (28 + 16)/7 = 44/7 hours.

∴ The correct answer is 44/7 hr.

Alternate Method

Given: Filling time Pipe A = 9 hr, Pipe B = 12 hr, Emptying time Pipe C = 18 hr.

PersonDaysTotal WorkEfficiency
Pipe A9364
Pipe B123
Pipe C18−2

⇒ Total capacity of tank = 36 units (LCM of 9, 12, 18).

⇒ Efficiency of (A + B + C) = 4 + 3 − 2 = 5 units/hr.

⇒ Water filled in 4 hours = 5 × 4 = 20 units.

⇒ Remaining capacity to be filled = 36 − 20 = 16 units.

⇒ Time taken by (A + B) to fill remaining part = 16 ÷ (4 + 3) = 16/7 hours.

⇒ Total time taken = 4 + 16/7 = 44/7 hours.

∴ The correct answer is 44/7 hr.

Additional Information

Inlet and Outlet Pipes

Inlet pipes add water (positive efficiency) while outlet pipes remove water (negative efficiency). Net work per hour is the algebraic sum of efficiencies.

Time and Work Relation

Total Work = Efficiency × Time. If a pipe can fill a tank in 'x' hours, its 1-hour work is 1/x of the total capacity.

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Question 868

RRB Group D 2025• Mathematics• Mathematics

If 8 solid spherical balls, each of radius 10 cm, are melted and recast into a single spherical ball, then what is the radius of the new ball so formed?

  1. AOption (a)

    20 cm

  2. BOption (b)

    15 cm

  3. COption (c)

    30 cm

  4. DOption (d)

    10 cm

View answer & explanation

Correct answer

Answer: (a)A.

20 cm

Why this answer is correct

Shortcut Trick

When multiple identical spheres are melted to form a single sphere, the volume remains constant.

Relationship: R3 = n × r3, where R is the new radius, n is the count, and r is the old radius.

R3 = 8 × 103

R3 = 8 × 1000 = 8000 ⇒ R = 20 cm

∴ The correct answer is 20 cm.

Alternate Method

Given:

Number of spherical balls (n) = 8

Radius of each small ball (r) = 10 cm

Formula Used:

Volume of a Sphere = 4/3 × π × radius3

Calculations:

⇒ Total volume of 8 small balls = 8 × (4/3 × π × 103)

⇒ Volume of the new single large ball = 4/3 × π × R3

⇒ According to the principle of conservation of volume:

⇒ 4/3 × π × R3 = 8 × 4/3 × π × 1000

⇒ R3 = 8 × 1000

⇒ R3 = 8000

⇒ R = √38000

⇒ R = 20 cm

∴ The correct answer is 20 cm.

Additional Information

Volume Conservation

When a solid is melted and recast into another shape, the total volume remains identical unless specified otherwise.

Surface Area of Sphere

The Total Surface Area (TSA) of a sphere is given by 4 × π × r2. Note that TSA changes during recasting.

Radius Ratio

If n spheres are melted into 1, the ratio of radii is R/r = n1/3. For n=8, R/r = 81/3 = 2.

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Question 869

RRB Group D 2025• Mathematics• Mathematics

The arithmetic mean of the observations 78, 66, 89, 55, 73, 45, 23, 46 and 29 is:

  1. AOption (a)

    56

  2. BOption (b)

    52

  3. COption (c)

    50

  4. DOption (d)

    48

View answer & explanation

Correct answer

Answer: (a)A.

56

Why this answer is correct

Shortcut Trick

Assume a base mean of 50 and find deviations: +28, +16, +39, +5, +23, −5, −27, −4, −21.

Calculate Net Deviation: 28 + 16 + 39 + 5 + 23 − 5 − 27 − 4 − 21 = +54.

Average Deviation = 54 ÷ 9 = +6.

Final Mean = Assumed Mean + Average Deviation = 50 + 6 = 56.

∴ The correct answer is 56.

Alternate Method

Given observations: 78, 66, 89, 55, 73, 45, 23, 46, 29

Number of observations (n) = 9

Formula Used: Arithmetic Mean = (Sum of all observations) ÷ (Total number of observations)

⇒ Total Sum = 78 + 66 + 89 + 55 + 73 + 45 + 23 + 46 + 29

⇒ Total Sum = 504

⇒ Arithmetic Mean = 504 ÷ 9

⇒ Arithmetic Mean = 56

∴ The correct answer is 56.

Additional Information

Properties of Arithmetic Mean

The sum of the deviations of all observations from their arithmetic mean is always zero: Σ(xi − Mean) = 0.

Effect of Operations

If each observation is increased, decreased, multiplied, or divided by a constant k, the mean also changes by the same operation with k.

Combined Mean Formula

For two groups with sizes n1, n2 and means x1, x2, the combined mean is (n1x1 + n2x2) ÷ (n1 + n2).

RRB Group D Official Paper (Held On: 27 Dec, 2025 Shift 1) (Previous Year Paper)·Mathematics
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Question 870

RRB Group D 2025• Mathematics• Mathematics

Find a single discount (approximately) equal to three consecutive discounts of 2%, 8% and 15%.

  1. AOption (a)

    26.77%

  2. BOption (b)

    23.36%

  3. COption (c)

    22.89%

  4. DOption (d)

    22.86%

View answer & explanation

Correct answer

Answer: (b)B.

23.36%

Why this answer is correct

Shortcut Trick

Total multiplier for consecutive discounts of 2%, 8%, and 15%.

Effective Multiplier = 0.98 × 0.92 × 0.85 = 0.76636.

Equivalent Discount% = (1 − 0.76636) × 100 = 23.364%.

Rounding to two decimal places, we get 23.36%.

∴ The correct answer is 23.36%.

Alternate Method

Given → Discounts are 2%, 8%, and 15%.
Formulas: Successive Discount = a + b − (a × b) ÷ 100.

⇒ First, combine 2% and 8%: 2 + 8 − (2 × 8) ÷ 100 = 10 − 0.16 = 9.84%.
⇒ Now, combine 9.84% and 15%: 9.84 + 15 − (9.84 × 15) ÷ 100.
⇒ Total = 24.84 − (147.6 ÷ 100) = 24.84 − 1.476.
⇒ Total Discount = 23.364%.

∴ The correct answer is 23.36%.

Additional Information

Single Equivalent Discount

It is the total reduction offered on the Marked Price through multiple stages. For three discounts a, b, and c, use the formula iteratively or the Multiplier Method.

Marked Price and Selling Price

The Selling Price (SP) after discount is: SP = MP × (100 − D1)/100 × (100 − D2)/100...

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Question 871

RRB Group D 2025• Mathematics• Mathematics

A total profit of ₹21,800 is to be distributed amongst A, B and C such that A : B = 4 : 15 and B : C = 9 : 3. The share (in ₹) of B in the profit is:

  1. AOption (a)

    13,525

  2. BOption (b)

    13,625

  3. COption (c)

    13,575

  4. DOption (d)

    13,675

View answer & explanation

Correct answer

Answer: (b)B.

13,625

Why this answer is correct

Shortcut Trick

Combine Ratio: A : B : C = (4 × 9) : (15 × 9) : (15 × 3) = 36 : 135 : 45.

Simplified Ratio: 12 : 45 : 15 ⇒ 4 : 15 : 5.

Total units = 4 + 15 + 5 = 24 units ⇒ ₹21,800.

B's share = (15 ÷ 24) × 21,800 = (5 ÷ 8) × 21,800 = 5 × 2725 = ₹13,625.

∴ The correct answer is ₹13,625.

Alternate Method

Given: Total Profit = ₹21,800, A : B = 4 : 15, B : C = 9 : 3.

Formula: Combined Ratio A : B : C = (A × B1) : (B1 × B2) : (B2 × C).

⇒ To equalize B, multiply A : B by 3 and B : C by 5.

⇒ A : B = 12 : 45.

⇒ B : C = 45 : 15.

⇒ A : B : C = 12 : 45 : 15 = 4 : 15 : 5.

⇒ Sum of ratio parts = 4 + 15 + 5 = 24.

⇒ B's share = (15 ÷ 24) × 21,800.

⇒ B's share = 0.625 × 21,800 = ₹13,625.

∴ The correct answer is ₹13,625.

Additional Information

Compound Ratio

When two or more ratios are multiplied together (a/b × c/d), the result is the compound ratio (ac/bd).

Partnership Profit Distribution

Profit is distributed in the ratio of (Capital × Time). If time is constant, profit ratio equals the investment ratio.

Proportion Rule

If a : b = c : d, then the product of extremes equals the product of means (a × d = b × c).

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Question 872

RRB Group D 2025• Mathematics• Mathematics

The price of milk has increased by 20%. By how much should the consumption be reduced to maintain the monthly expenditure constant on milk?

  1. AOption (a)

    \( 16\frac{2}{7}% \)

  2. BOption (b)

    \( 16\frac{4}{7}% \)

  3. COption (c)

    \( 16\frac{1}{3}% \)

  4. DOption (d)

    \( 16\frac{2}{3}% \)

View answer & explanation

Correct answer

Answer: (d)D.

\( 16\frac{2}{3}% \)

Why this answer is correct

Shortcut Trick

Use the direct formula for reduction in consumption: [r / (100 + r)] × 100%

Here, increase rate r = 20%.

Reduction = [20 / (100 + 20)] × 100 = (20 / 120) × 100 = 1/6 × 100

Calculation: 100 / 6 = 16(2/3)%

∴ The correct answer is 16(2/3)%.

Alternate Method

Given:

Initial Price of milk = 100 units

Increased Price = 100 + 20% of 100 = 120 units

Formula Used:

Expenditure = Price × Consumption

To keep Expenditure constant, the new consumption must be brought back to the base of the new price.

⇒ Required reduction in consumption = New Price − Old Price = 120 − 100 = 20 units

⇒ Percentage reduction = (Reduction / New Price) × 100

⇒ Percentage reduction = (20 / 120) × 100

⇒ Percentage reduction = (1 / 6) × 100

⇒ Percentage reduction = 16.66% or 16(2/3)%

∴ The correct answer is 16(2/3)%.

Additional Information

Price-Consumption Relationship

When Expenditure is constant, Price is inversely proportional to Consumption (P ∝ 1/C).

Price Decrease Case

If price decreases by r%, the increase in consumption to keep expenditure constant is [r / (100 − r)] × 100%.

Fraction Conversion

20% increase is 1/5. For constant product, if one factor increases by 1/n, the other must decrease by 1/(n+1). Here, 1/(5+1) = 1/6 = 16(2/3)%.

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Question 873

RRB Group D 2025• Mathematics• Mathematics

Which of the options has the two prime numbers whose product is the biggest even number less than 30?805

  1. AOption (a)

    \( 3 \text{ and } 11 \)

  2. BOption (b)

    \( 3 \text{ and } 7 \)

  3. COption (c)

    \( 2 \text{ and } 13 \)

  4. DOption (d)

    \( 2 \text{ and } 5 \)

View answer & explanation

Correct answer

Answer: (c)C.

\( 2 \text{ and } 13 \)

Why this answer is correct

Shortcut Trick

The biggest even number less than 30 is 28.

Check products from options:

(1) 33, (2) 21, (3) 26, (4) 10.

The largest even product less than 28 (or specifically less than 30) among options is 26.

∴ The correct answer is 2 and 13.

Alternate Method

Given: Product must be an even number less than 30.

Property: To get an even product from two prime numbers, one of the numbers must be the only even prime, which is 2 (since Odd × Odd = Odd and Even × Any = Even).

⇒ Target: Largest product P < 30 where P is even.

⇒ Option 1: 3 × 11 = 33 (Odd, > 30) ×

⇒ Option 2: 3 × 7 = 21 (Odd) ×

⇒ Option 3: 2 × 13 = 26 (Even, < 30) ✓

⇒ Option 4: 2 × 5 = 10 (Even, < 30) × [26 is larger than 10]

∴ The correct answer is 2 and 13.

Additional Information

Even Prime Number

The number 2 is the only even prime number. All other prime numbers are odd.

Product Parity Rules

Odd × Odd = Odd; Even × Odd = Even; Even × Even = Even.

Prime Number Definition

A natural number greater than 1 that has no positive divisors other than 1 and itself.

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Question 874

RRB Group D 2025• Mathematics• Mathematics

The sides of a triangle are 35 cm, 44 cm and 75 cm. What is the length of its altitude corresponding to the side with the length of 44 cm?

  1. AOption (a)

    65 cm

  2. BOption (b)

    58 cm

  3. COption (c)

    14 cm

  4. DOption (d)

    21 cm

View answer & explanation

Correct answer

Answer: (d)D.

21 cm

Why this answer is correct

Shortcut Trick

Calculate the semi-perimeter (s) of the triangle: s = (35 + 44 + 75) ÷ 2 = 77 cm.

Find the Area using Heron's Formula: Area = √(77 × (77−35) × (77−44) × (77−75)) = √(77 × 42 × 33 × 2).

Area = √(7 × 11 × 7 × 6 × 3 × 11 × 2) = 7 × 11 × 6 = 462 cm2.

Altitude (h) corresponding to the 44 cm base = (2 × Area) ÷ base = (2 × 462) ÷ 44 = 21 cm.

∴ The correct answer is 21 cm.

Alternate Method

Given: Sides of the triangle are a = 35 cm, b = 44 cm, and c = 75 cm.

Formula Used:

  1. Semi-perimeter (s) = (a + b + c) ÷ 2
  2. Area = √(s(s − a)(s − b)(s − c))
  3. Area = (1 ÷ 2) × base × altitude

Calculations:

⇒ s = (35 + 44 + 75) ÷ 2

⇒ s = 154 ÷ 2 = 77 cm

⇒ Area = √(77 × (77 − 35) × (77 − 44) × (77 − 75))

⇒ Area = √(77 × 42 × 33 × 2)

⇒ Area = √((7 × 11) × (7 × 6) × (11 × 3) × 2)

⇒ Area = √(72 × 112 × 62) = 7 × 11 × 6 = 462 cm2

⇒ 462 = (1 ÷ 2) × 44 × altitude

⇒ 462 = 22 × altitude

⇒ altitude = 462 ÷ 22 = 21 cm

∴ The correct answer is 21 cm.

Additional Information

Heron's Formula for Area

Used to find the area of a triangle when all three sides are known: Area = √(s(s−a)(s−b)(s−c)), where s is the semi-perimeter.

Relationship between Area and Altitude

For any side taken as the base, the area is always 1/2 × base × corresponding height. Thus, height = (2 × Area) ÷ base.

Triangle Inequality Theorem

A triangle is valid only if the sum of any two sides is greater than the third side (e.g., 35 + 44 = 79, which is > 75).

RRB Group D Official Paper (Held On: 27 Dec, 2025 Shift 1) (Previous Year Paper)·Mathematics
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Question 875

RRB Group D 2025• Mathematics• Mathematics

Solve: \( \frac{(100.5)^2 - (79.2)^2}{100.5 + 79.2} \)

  1. AOption (a)

    23.5

  2. BOption (b)

    22.4

  3. COption (c)

    20.2

  4. DOption (d)

    21.3

View answer & explanation

Correct answer

Answer: (d)D.

21.3

Why this answer is correct

Shortcut Trick

The given expression follows the algebraic identity (a2 − b2) / (a + b) = (a − b).

Here, let a = 100.5 and b = 79.2.

The solution is simply the difference between the two numbers: 100.5 − 79.2 = 21.3.

∴ The correct answer is 21.3.

Alternate Method

Given:

Expression: ((100.5)2 − (79.2)2) / (100.5 + 79.2)

Formula Used:

Algebraic Identity: a2 − b2 = (a + b)(a − b)

Calculations:

⇒ Let a = 100.5 and b = 79.2.

⇒ Numerator = (100.5)2 − (79.2)2 = (100.5 + 79.2) × (100.5 − 79.2)

⇒ Substituting this into the main expression:

⇒ [(100.5 + 79.2) × (100.5 − 79.2)] / (100.5 + 79.2)

⇒ 100.5 − 79.2 (Cancelling the common term 100.5 + 79.2)

⇒ 21.3

The calculated value corresponds to option (4).

∴ The correct answer is 21.3.

Additional Information

Difference of Squares

The identity a2 − b2 = (a + b)(a − b) is used to simplify expressions involving squares of two numbers.

Square of a Sum

The formula (a + b)2 = a2 + 2ab + b2 expands the square of the sum of two variables.

Square of a Difference

The formula (a − b)2 = a2 − 2ab + b2 expands the square of the difference between two variables.

Fraction Simplification

If the numerator and denominator share a common factor, they can be cancelled: (x × y) / x = y, provided x ≠ 0.

RRB Group D Official Paper (Held On: 26 Dec, 2025 Shift 3) (Previous Year Paper)·Mathematics
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Question 876

RRB Group D 2025• Mathematics• Mathematics

Find the value of \( \sqrt{8}+2\sqrt{32}-\sqrt{128}+2\sqrt{50} \).

  1. AOption (a)

    \( \sqrt{2} \)

  2. BOption (b)

    \( 4\sqrt{2} \)

  3. COption (c)

    \( 3\sqrt{2} \)

  4. DOption (d)

    \( 12\sqrt{2} \)

View answer & explanation

Correct answer

Answer: (d)D.

\( 12\sqrt{2} \)

Why this answer is correct

Shortcut Trick

Convert all into same root form

√8 = 2√2, √32 = 4√2, √128 = 8√2, √50 = 5√2

Expression = 2√2 + 2×4√2 − 8√2 + 2×5√2

= (2 + 8 − 8 + 10)√2 = 12√2

∴ Answer = 12√2

Alternate Method

Given:

√8 + 2√32 − √128 + 2√50

Concept Used:

Simplification of surds

Calculation:

⇒ √8 = √(4×2) = 2√2

⇒ √32 = √(16×2) = 4√2

⇒ √128 = √(64×2) = 8√2

⇒ √50 = √(25×2) = 5√2

⇒ Substitute values

⇒ = 2√2 + 2(4√2) − 8√2 + 2(5√2)

⇒ = 2√2 + 8√2 − 8√2 + 10√2

⇒ = (2 + 8 − 8 + 10)√2

⇒ = 12√2

∴ The correct answer is 12√2.

Additional Information

Surd Simplification

√(a×b) = √a × √b

Like Terms

Only same radicals can be added/subtracted

Perfect Squares

Extract perfect square factors for simplification

RRB Group D Official Paper (Held On: 26 Dec, 2025 Shift 3) (Previous Year Paper)·Mathematics
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Question 877

RRB Group D 2025• Mathematics• Mathematics

What percent is \( \frac{1}{20} \) of \( \frac{11}{20} \)? (Round off to two decimal places.)

  1. AOption (a)

    9.09%

  2. BOption (b)

    18.18%

  3. COption (c)

    24.09%

  4. DOption (d)

    19.09%

View answer & explanation

Correct answer

Answer: (a)A.

9.09%

Why this answer is correct

Shortcut Trick

Required percentage = (Value ÷ Base Value) × 100

Since both fractions have the same denominator (20), the percentage is simply (Numerator 1 ÷ Numerator 2) × 100.

Required % = (1 ÷ 11) × 100 ≈ 9.09%

∴ The correct answer is 9.09%.

Alternate Method

Given:

First value = 1/20

Second value (Base) = 11/20

Formula Used:

Percentage = (A/B) × 100

Calculations:

⇒ Required Percentage = [(1/20) ÷ (11/20)] × 100

⇒ Required Percentage = (1/20 × 20/11) × 100

⇒ Required Percentage = (1/11) × 100

⇒ Required Percentage = 100 ÷ 11

⇒ Required Percentage = 9.090909...

⇒ Required Percentage ≈ 9.09%

∴ The correct answer is 9.09%.

Additional Information

Fraction to Percentage Conversion

To convert any fraction x/y into a percentage, multiply the fraction by 100 and add the % symbol.

Reciprocal Percentages

Knowing common reciprocals like 1/11 ≈ 9.09% and 1/9 ≈ 11.11% helps in solving Simplification and Percentage questions faster.

Percentage Change

Percentage change = [(New Value − Original Value) ÷ Original Value] × 100.

RRB Group D Official Paper (Held On: 26 Dec, 2025 Shift 3) (Previous Year Paper)·Mathematics
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Question 878

RRB Group D 2025• Mathematics• Mathematics

If 20 percent of a number is added to 60, the result is that number. 70 percent of that number is ................

  1. AOption (a)

    62.5

  2. BOption (b)

    72.5

  3. COption (c)

    52.5

  4. DOption (d)

    82.5

View answer & explanation

Correct answer

Answer: (c)C.

52.5

Why this answer is correct

Shortcut Trick

0.2x + 60 = x

0.8x = 60 ⇒ x = 75

70% of x = 0.7 × 75

= 52.5

∴ Answer = 52.5

Alternate Method

Given:

20% of a number when added to 60 gives the number

Formula used:

Percentage = (value ÷ 100) × number

Calculation:

⇒ Let the number be x

⇒ 20% of x = (20/100) × x = 0.2x

⇒ According to question

⇒ 0.2x + 60 = x

⇒ x − 0.2x = 60

⇒ 0.8x = 60

⇒ x = 60 ÷ 0.8 = 75

⇒ Required percentage = 70% of 75

⇒ = (70/100) × 75

⇒ = 52.5

∴ The correct answer is 52.5.

Additional Information

Percentage Formula

x% of number = (x/100) × number

Equation Formation

Translate statement into linear equation

Decimal Conversion

20% = 0.2, 70% = 0.7

RRB Group D Official Paper (Held On: 26 Dec, 2025 Shift 3) (Previous Year Paper)·Mathematics
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Question 879

RRB Group D 2025• Mathematics• Mathematics

A person buys a book for ₹ 300 and sells it for ₹ 335. What will be his profit percentage?

  1. AOption (a)

    \( 11\frac{4}{3}% \)

  2. BOption (b)

    \( 11\frac{5}{3}% \)

  3. COption (c)

    \( 11\frac{1}{3}% \)

  4. DOption (d)

    \( 11\frac{2}{3}% \)

View answer & explanation

Correct answer

Answer: (d)D.

\( 11\frac{2}{3}% \)

Why this answer is correct

Shortcut Trick

Profit = SP − CP = 335 − 300 = 35.

Profit % = (Profit ÷ CP) × 100.

Profit % = (35 ÷ 300) × 100 = 35 ÷ 3 = 112/3%.

∴ The correct answer is 11(2)/(3)%.

Alternate Method

Given → Cost Price (CP) = ₹ 300, Selling Price (SP) = ₹ 335.
Formulas: Profit = SP − CP | Profit% = (Profit ÷ CP) × 100

→ Profit = 335 − 300 = 35
→ Profit % = (35 ÷ 300) × 100
→ Profit % = 35 ÷ 3 = 11.66...%
→ In fraction form, 35/3 = 112/3%

∴ The correct answer is 11(2)/(3)%.

Additional Information

Profit and Loss Basics

Profit occurs when Selling Price (SP) is greater than Cost Price (CP). Loss occurs when CP > SP.

Percentage Calculation

Profit or Loss percentage is always calculated on the Cost Price (CP) unless stated otherwise.

RRB Group D Official Paper (Held On: 26 Dec, 2025 Shift 3) (Previous Year Paper)·Mathematics
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Question 880

RRB Group D 2025• Mathematics• Mathematics

\( ABCD \) is a parallelogram. \( P \) and Q are two points lying on the sides DC and AD respectively. The area of \( \Delta APB \) ​​is equal to __________________.

  1. AOption (a)

    half the area of ​​the quadrilateral \( ABPD \)

  2. BOption (b)

    the area of \( \Delta DQC \) के क्षेत्रफल

  3. COption (c)

    the area of \( (\Delta BQC + \Delta ABQ) \)

  4. DOption (d)

    the area of \( \Delta BQC \)

View answer & explanation

Correct answer

Answer: (d)D.

the area of \( \Delta BQC \)

Why this answer is correct

Shortcut Trick

The area of a triangle sharing the same base and lying between the same parallel lines as a parallelogram is always half the area of that parallelogram.

Area(Δ APB) = 1/2 × Area(ABCD) (since they share base AB and lie between AB || CD).

Area(Δ BQC) = 1/2 × Area(ABCD) (since they share base BC and lie between BC || AD).

Since both triangles are equal to half of the same parallelogram, their areas must be equal.

∴ The correct answer is the area of Δ BQC.

Alternate Method

Given:ABCD is a parallelogram. P is a point on side DC and Q is a point on side AD.

Formula Used: Area of triangle = 1/2 × base × height; Area of parallelogram = base × height.

⇒ Area(Δ APB) = 1/2 × AB × (height of parallelogram with respect to base AB)

⇒ Area(ABCD) = AB × (height of parallelogram with respect to base AB)

⇒ Area(Δ APB) = 1/2 × Area(ABCD) --- (i)

⇒ Area(Δ BQC) = 1/2 × BC × (height of parallelogram with respect to base BC)

⇒ Area(ABCD) = BC × (height of parallelogram with respect to base BC)

⇒ Area(Δ BQC) = 1/2 × Area(ABCD) --- (ii)

⇒ From equations (i) and (ii), we get: Area(Δ APB) = Area(Δ BQC)

∴ The correct answer is the area of Δ BQC.

Additional Information

Area of Parallelogram

The area of a parallelogram is given by the product of its base and the corresponding altitude (height).

Triangle and Parallelogram Relationship

When a triangle and a parallelogram are on the same base and between the same parallels, the area of the triangle is half the area of the parallelogram.

Parallelogram Properties

In a parallelogram, opposite sides are parallel and equal, and diagonals bisect each other, dividing the parallelogram into two triangles of equal area.

How should I prepare for Quantitative Aptitude in RRB Group D?

Solving previous year questions by topic helps identify recurring concepts, question patterns, and frequently asked sub-topics. Attempt each question, review the step-by-step explanation, and note down key formulas or facts for quick revision before the exam.