Sainik School Entrance Exam 2021 Solved Paper

(b) $\mathit{A}$ can do a work in 25 days.
∴ One day work of $\mathit{A}=\frac{1}{25}$
$\mathit{B}$ can do the same work in 20 days.
∴ $1$ day work of $\mathit{B}=\frac{1}{20}$
5 days work of $\mathit{A}$ and $\mathit{B}$ together
$=\frac{5}{25}+\frac{5}{20}=\frac{1}{5}+\frac{1}{4}=\frac{9}{20}.$
Remaining work $=1-\frac{9}{20}=\frac{11}{20}$
$\mathit{B}$, finishes the remaining work in $=\frac{\frac{11}{20}}{\frac{1}{20}}=11$ days.