A can do a piece of work in 72 days and B in 90 days. They worked together for 30 days and then B left. Find the days taken by A to finish the remaining work.
Show answer & explanation
Correct answer: A
Explanation
The correct answer is Option 1 i.e. 18 days
A can finish a work in 72 days and B can finish that in 90 days.
Total work to be done = LCM of 72, 90 = 360 units
Work done by A in a day = 360/72 = 5 units
Amount of work done by B in a day = 360/90 = 4 units
Amount of work done by them together in 30 days = 30(4 + 5) = 30(9) = 270 units
Remaining work = 360 - 270 = 90 units
Remaining work done by A in = 90/5 = 18 days