Question

A and b can do a work in 72 days , if last 20 days a alone does the work it will complete in 40 days.How many days will it take for a to do the work all alone ?

Answer 1

If u want to solve other questions here is second formula-

$m1d1h1 = m2d2h2 \\ number \: of \: men = m1 \\ numer \: of \: days \: taken \: by \: men = d1 \\ hours \: taken \: by \: men = h1$