Question

Choose the correct answer from the alternative given.
A and B can together finish a work in $30$ days. They worked at it for $20$ days and then B left The remaining work was done by A alone in $20$ more days. A alone can finish the work in

Answer 1

Let the total work be $60$ units. (LCM of $30$ and $20$) So ,A and B i.e. A + B do $\frac{60}{30}$. $=2$ units/day.

As A and B worked for $20$ days. they completed $20$ $\times$ $2=40$ units of work.
Work left is $60-40=20$ units, which is completed by A in 20 more days.
So, A does $\frac{20}{20}$ $=1$ unit/day.
A alone can finish the work in $\frac{60}{1}$ $=60$ days.