Question

A can do a piece of work in 15 days
and B in 20 days. If they together
work on it for 4 days, then the frac-
tion of the work that is left is :
A एक काम को 15 दिनों में तथा B 20 दिनों में
कर सकता है। यदि वे 4 दिनों तक एक साथ काम
करते है तो अब काम कितना हिस्सा बचा हुआ है।​

Answer 1

$\huge\text{\underline{Answer}}$

The total amount of work is equal to L. C. M of (15 and 20) which is 60

A can do a peice of work in 15 days

then, work done by A in 1 day is $\bold{\frac{1}{15} part \: of \: work \: }$

B can do a peice of work in 20 days

work done by B in 1 day is $\bold{\frac{1}{20} part of work }$

Now,

Both A and B (A + B) work together in 4 days .

The work done by both ( A + B) in one day $\bold{\frac{1}{15}+\frac{1}{20} part of work }$

$\implies$ $\bold{ \frac{15 + 20}{300} }$

$\implies$ $\bold{ = \frac{35}{300} }$

Now, they both work together in 4 days.

$\implies$ $\frac{35}{300} ×4$

$\implies$ $\frac{7}{15}$

Hence , total work left is

$= 1 - \frac{7}{15}$

$= \frac{15 - 7}{15}$

$= \frac{8}{15} part \: of \: work \:$