Query Detail : RBI Grade B Phase I

. A and B can together finish a piece of work in 20 days. If B starts working and after 15 days is replaced by A, A can finish the remaining work in 24 days. No. of days in which A and B can finish the whole work alone. Correct answer: A=36 and B=45 days.
Garima,   November 5th 2019,  
RBI Grade B Phase I


(A+B)*20 = B*15+A*24

So 20A+20B =15B+24A

4A=5B

So A:B = 5:4 let A can do 5 units daily & B can do 4 units daily

So toatl work =(A+B)*20 = (5+4)*20 = 180 units

A can do this alone in = 180/5 = 36 days

B can do this alone in = 180/4 = 45 days