Question

A can complete a piece of work in 4 days while B alone can complete it in 7 days. If A starts working and left after 2 days, in how many days can B alone complete the remaining piece of work? 

1. 5 days
2. 4.5 days
3. 3 days
4. 3.5 days

Answer 1

Correct Answer - Option 4 : 3.5 days

Given:

A can complete a piece of work in 4 days.

B alone can complete it in 7 days.

A starts working and left after 2 days.

Concepts used:

1 day work done by individual = Work/time

Time = Work/Efficiency

Calculation:

1 day work done by individual = Work/time

⇒ 1 day work of A = 1/4

⇒ 2 days work of A = 2/4 = 1/2

Remaining work = 1 – (1/2) = 1/2

B alone can complete the work in 7 days.

⇒ Time taken by B to complete 1 work = 7 days

⇒ Time taken by B to complete 1/2 work = (1/2) × 7 days = 3.5 days

∴ B alone can complete remaining piece of work in 3.5 days.