Question

A and B can do a piece of work in 20 days and B in 15 days. They work together for 2 days and then A goes away. In how many days will B finish the remaining work?

Answer 1

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

B's one day work $=\frac{1}{15}$

A and B's 2 days works $=\frac{1}{20}\times 2=\frac{1}{10}$

Remaining work $=1-\frac{1}{10}=\frac{10-1}{10}=\frac{9}{10}$

Now B's cand do $\frac{1}{15}$ work in =1 day

$\therefore$ B will do $\frac{9}{10}$ work in $=\frac{1\times 15}{1}\times \frac{9}{10}$

$=\frac{27}{2}=13\frac{1}{2}$ days