Question

A can do a work in 15days and b in 20 days if they together work on it for 4 days , then the fraction of the work that is left is

Answer 1

time taken by A to do the work=15days. time taken by B to do the work=20days. A 1 day work =1/15. B 1day work=1/20. (A+B ) 1 day work=1/15+1/20=7/60. (A+B) 4days work=4*7/60=7/15. Remaining work=1-7/15=8/15