Question

Abdul can paint a wall in 20 days . He starts the work but has to stop it in 5 days. Rohan then completes the work in 12 days. How long would Rohan have taken to do the entire work by himself?

Answer 1

Abdul can paint a wall in 20 days.
$\therefore$ Work done by Abdul in one day $=\frac{1}{20}$
$\therefore$ Work done by Abdul in five days $\frac{1}{20}\times 5=\frac{1}{4}$
Remaining part of work =$1-\frac{1}{4}=\frac{3}{4}$
Rohan then completes the work in 12 days
Work done by Rohan in one day
=$\frac{Remainingwork}{Numberofdayshetooktocompletethework}$
$=\frac{3}{4}÷12=\frac{3}{4}\times \frac{1}{12}=\frac{1}{16}$
$\therefore$ Work done by Rohan in one day $=\frac{1}{16}$
$\therefore$ Rohan would have taken 16 days to complete the entire work by himself.