Question

A and B can finish a work in 20 days. A alone can do $\frac{1}{5}$th of the work in 12 days. In how many days can B alone do it?

Answer 1

A and B's one day work $=\frac{1}{20}$

A's 12 days work $=\frac{1}{5}$

A's 1 days work $=\frac{1}{5}\times \frac{1}{12}=\frac{1}{60}$

Then B's 1 day work $=\frac{1}{20}-\frac{1}{60}$

$=\frac{3-1}{60}=\frac{2}{60}=\frac{1}{30}$

$\therefore$ B can do the work in =30 days