A completes 80% of a work in 20 days. Then B joins A and they complete the remaining work in 3 days. How long will B alone take to complete the whole work?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is Option 1 i.e. days.
A completes 80% of a work in 20 days
A completes 100% of the work = 20 × 100/80 = 25 days
80% of the work = 4/5
Remaining work = (1 - 4/5) = 1/5
So, 1/5 of the work done by both in 3 days
Hence, the complete work done by A and B will be in 15 days
L.C.M(25, 15) = 75
The efficiency of A = 75/25 = 3 units and,
The efficiency of A and B = 75/15 = 5 units
Hence, the efficiency of B = 2 units
Time taken by B to complete the whole work = 75/2 = days