A can finish 80% of a task in 12 days, and B can finish 20% of the same task in 2 days. They started the task together, but B left after 2 days, and A continued to work. In how many days was the entire task completed?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 12.
Time taken by A to complete the whole work = 12 × = 15 days
Time taken by B to complete the whole work = 2 × = 10 days
LCM(15, 10) = 30
The efficiency of A = 30/15 = 2 units
The efficiency of B = 30/10 = 3 units
Work done by both in two days = 2(2 + 3) = 2 × 5 = 10 units
Remaining = 30 - 10 = 20 units
Time taken by A to complete the remaining work = 20/2 = 10 days
Total time = 2 + 10 = 12 days