A can do a piece of work in 2 days, and B can do five times the same work in 15 days when they work for ten hours a day. If they work together, then how many hours in addition to a days of work will they require to complete the work?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 2.
A and B work for 10 hours a day
A complete the work in 2 days, means A work for 20 hours
B completed 5 times the same work in 15 days, which means B completes the same work in 3 days
B work for 30 hours
Total work = LCM of (20 and 30) = 60 units
The efficiency of A = 60/20 = 3 units/hour
The efficiency of B = 60/30 = 2 units/hour
Total efficiency = 3 + 2 = 5 units/hour
Time taken by them to complete 60 units of work = 60/5 = 12 hours
Extra time devoted = 12 - 10 = 2 hours