Question:
Anil can do a piece of work in 5 days and Ankur in 4 days. How long will they take to do the same work, if they work together?
Solution:
Time taken by Anil to do the work $=5$ days
Time taken by Ankur to do the work $=4$ days
$\therefore$ Work done by Anil in 1 day $=\frac{1}{5}$
Work done by Ankur in 1 day $=\frac{1}{4}$
$\therefore$ Work done by Anil and Ankur in one day $=\frac{1}{5}+\frac{1}{4}$
$=\frac{4+5}{20}=\frac{9}{20}$
Thus, Anil and Ankur can do the work in $\frac{20}{9}$ days i. e. $2 \frac{2}{9}$ days.