A and B can separately finish a work in 15 and 20 days, respectively. A starts the work and B joins him from the fifth day. How much time will it take to finish the complete work?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 4 i.e. 10 days.
Total work = LCM of 15 and 20 = 60
Efficiency: A = 60/15 = 4 and B = 60/20 = 3
Work done by A in 4 days = 4 × 4 = 16
Remaining work = 60 - 16 = 44
Time required for remaining work = 44/(4 + 3) = days
Total time = 4 + days