Question

A can do a work in 15 days and B in 20 days if they work on together for 4 days then the fraction of the work that is left is

Answer 1

Solution:-
A can do a piece of work in 15 days.
One day work of A =1/15
B can do a piece of work in 20 days
One day work of B =1/20

(A+B)'s one day work=
$= > \frac{1}{15} + \frac{1}{24} \\ = > \frac{4 + 3}{60} \\ = > \frac{7}{60}$
They work for 4 days.
$= > \frac{7}{60} \times 4 \\ = > \frac{7}{15}$
So,7/15 of the work is done by A and B
Remain work=
$= > 1 - \frac{7}{15} \\ = > \frac{15 - 7}{15} \\ = > \frac{8}{15}$
Hence,8/15 of the work is left.