Correct Answer - Option 4 : 5.6 days
Given:
A alone can complete a piece of work in 8 days.
B alone can complete same piece of work in 12 days.
A starts working and B joins A 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 = 1/8
⇒ 2 days work of A = 2/8 = 1/4
⇒ Remaining work = 1 – (1/4) = 3/4
1 day work of B = 1/12
Remaining work is completed by A and B together.
⇒ 1 day work of A and B = (1/8) + (1/12) = 5/24
⇒ Time taken to complete 5/24 work = 1
Time = Work/Efficiency
⇒ Time taken to complete 3/4 work = 3/4 ÷ (5/24) = 18/5 days = 3.6 days
⇒ Total time taken in completing the work = 2 + 3.6 days = 5.6 days
∴ Total work is completed in 5.6 days.
