Question

A can do a work in 15 days and B in 20 days. If they work
on it together for 4 days, then the fraction of the work that is
left is--​

Answer 1

suppose total work is1

A=1/15 & B=1/20 for one day work

when both work together

(A+B)= (1/15)+(1/20)=7/60

for4 days

(7/60)x4=7/15

for remaining work

1-(7/15)=8/15

Answer (8/15)

HOPE THIS MAY HELP

Answer 2

Step-by-step explanation:

let total work is 1

A can do a work in 15 days

so 1 day work 1/15

B can do a work in 20 days

so 1 day work 1/20

Now A and B both can 1 day work is (1/15+1/20) =7/60

so 4 days work = 7/60 ×4= 7/15

Now left work is( 1- 7/15)=8/15