Question

Joseph and peter can complete a work in 20 hours and 25 hours respectively. Find:
Time taken by peter to complete the remaining work.

Answer 1

Time taken by joseph complete a work = 20 hours.

Time taken by peter to complete a work = 25 hours

Joseph's one hour work = 1/20

Peter's one hour work=1/25

So both joseph' and peter's work in one hour = 1/20 + 1/25

taking LCM = ( 5+ 4 )/ 100 = 9/100

work done by both together in 4 hrs = $\frac{9}{100}\times 4=\frac{9}{25}$

Work left after both worked together for 4 hrs $=1-\frac{9}{25}=\frac{(25-9)}{25}=\frac{16}{25}$

Time taken by peter to complete the remaining work = $\frac{16/25}{1/25}=25\times 16/25$ = 16 hours