Correct Answer - Option 3 : 63
Given:
The ratio of working efficiency of A and B = 1 ∶ 3
Time taken by C to complete the work = 30 days
Time taken by B to complete the work = 30% less time than C
Formula used:
Total work done = Efficiency × Time taken to complete the work
Calculation:
Time taken by B to complete the work = 30% less time than C
⇒ 30 – [(30/100) × 30]
⇒ 30 – 9
⇒ 21 days
Let the efficiency of A and B be 1a and 3a
Time required by B to finish the work = 21 days.
Total work done by B = Efficiency × Time taken to complete the work
⇒ 3a × 21
⇒ 63a unit
Time taken by A to finish the work = Total work/Efficiency
⇒ 63a/1a
⇒ 63 days
∴ Time taken by A to finish the work is 63 days
