What is the greatest length of a measuring rod that can exactly measure three fabric pieces of lengths 7 m 35 cm, 9 m 45 cm, and 10 m 50 cm?
- AOption (a)
1 m 15 cm
- BOption (b)
1 m 20 cm
- COption (c)
1 m 5 cm
- DOption (d)
1 m 25 cm
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Correct answer
1 m 5 cm
Why this answer is correct
Shortcut Trick
Convert all units to cm: 735 cm, 945 cm, and 1050 cm.
To find the greatest length, find the HCF using the difference method.
Difference 1 = 945 − 735 = 210; Difference 2 = 1050 − 945 = 105.
Since 105 divides 735 (105 × 7), 945 (105 × 9), and 1050 (105 × 10), the HCF is 105 cm.
105 cm = 100 cm + 5 cm = 1 m 5 cm.
∴ The correct answer is 1 m 5 cm.
Alternate Method
Given: Fabric lengths are 7 m 35 cm, 9 m 45 cm, and 10 m 50 cm.
Formula Used: The greatest length that can exactly measure several lengths is their Highest Common Factor (HCF).
⇒ Conversion to cm: (1 m = 100 cm)
⇒ L1 = 7 × 100 + 35 = 735 cm
⇒ L2 = 9 × 100 + 45 = 945 cm
⇒ L3 = 10 × 100 + 50 = 1050 cm
⇒ Prime Factorization:
⇒ 735 = 3 × 5 × 7 × 7
⇒ 945 = 3 × 3 × 3 × 5 × 7
⇒ 1050 = 2 × 3 × 5 × 5 × 7
⇒ Common factors = 3, 5, 7
⇒ HCF = 3 × 5 × 7 = 105 cm
⇒ Converting back to meters: 105 cm = 100 cm + 5 cm = 1 m 5 cm
∴ The correct answer is 1 m 5 cm.
Additional Information
Highest Common Factor (HCF)
The HCF of two or more numbers is the largest number that divides each of them without leaving a remainder. In measurement problems, the greatest possible size is always the HCF.
Least Common Multiple (LCM)
The LCM is the smallest number that is a multiple of all the given numbers. It is used for finding simultaneous occurrences or the smallest common container.
Unit Conversion
Always ensure all measurements are in the same standard unit before performing calculations. 1 meter = 100 centimeters; 1 kilometer = 1000 meters.