In the question, two quantities I, and II are given. You have to solve both the quantities and establish the correct relation between Quantity - I, and Quantity - II and choose the correct option accordingly.
Quantity I:
A can do a work in 24 days and B can do it in 36 days. They work together for 6 days, then B leaves. Find total time to complete work
Quantity II:
A can do a work in 30 days and B can do it in 20 days. They work together for 5 days, then A leaves. Find total time to complete work
- AOption (a)
Quantity I β€ Quantity II
- BOption (b)
Quantity I > Quantity II
- COption (c)
Quantity I < Quantity II
- DOption (d)
Quantity I = Quantity II
- EOption (e)
Quantity I β₯ Quantity II
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Correct answer
Quantity I > Quantity II
Why this answer is correct
Shortcut Trick
Quantity I: Total work (LCM of 24, 36) = 72. Efficiencies: A = 3, B = 2. Together 6 days = 6 Γ 5 = 30. Remaining = 42. Time by A = 42 Γ· 3 = 14. Total = 6 + 14 = 20 days.
Quantity II: Total work (LCM of 30, 20) = 60. Efficiencies: A = 2, B = 3. Together 5 days = 5 Γ 5 = 25. Remaining = 35. Time by B = 35 Γ· 3 = 11.67. Total = 5 + 11.67 = 16.67 days.
Comparing both: 20 days > 16.67 days.
β΄ The correct answer is Quantity I > Quantity II.
Alternate Method
Quantity I:
Person
Days
Total Work
Efficiency
A
24
72
3
B
36
2
β Combined efficiency of A and B = 3 + 2 = 5 units/day.
β Work done in 6 days = 6 Γ 5 = 30 units.
β Remaining work = 72 β 30 = 42 units.
β Time taken by A to finish remaining work = 42 Γ· 3 = 14 days.
β Total time = 6 + 14 = 20 days.
Quantity II:
Person
Days
Total Work
Efficiency
A
30
60
2
B
20
3
β Combined efficiency of A and B = 2 + 3 = 5 units/day.
β Work done in 5 days = 5 Γ 5 = 25 units.
β Remaining work = 60 β 25 = 35 units.
β Time taken by B to finish remaining work = 35 Γ· 3 = 11.67 days.
β Total time = 5 + 11.67 = 16.67 days.
Comparison: 20 > 16.67 β Quantity I > Quantity II.
β΄ The correct answer is Quantity I > Quantity II.
Additional Information
LCM Method for Work
Total work is assumed as the LCM of time taken by individuals to simplify efficiency calculations as integers.
Work and Efficiency Relation
Total Work = Efficiency Γ Time. If total work is constant, efficiency is inversely proportional to time taken.
Leaving and Joining
For such problems, calculate work done during the period of togetherness and subtract from total work to find the remainder.