A can do a work in 12 days, B in 16 days. A works for 3 days, then B joins and they complete the remaining work together.
How many total days did it take to complete the work?
Show answer & explanation
Correct answer: C
Explanation
A's 1-day work efficiency = 1/12
B's 1-day work efficiency = 1/16
Work done by A in 3 days = 3/12 = 1/4
Remaining work = 1 − 1/4 = 3/4
Combined 1-day work efficiency of A and B
= 1/12 + 1/16 = 7/48
Time taken to complete the remaining work -
= (3/4) ÷ (7/48)
= 36/7 days = 5 1/7 days
Total time = 3 + 5 1/7 = 8 1/7 = 8.1days