Question

A can do a work in 15 days and B in 20 days. If they work on it together for 4 days, then the fraction of the work
that is left is :
Select one:
O a 7/15
b. 8/15
O c. 1/10
Od 1/4​

Answer 1

Answer:

8/15. This is the answer

Answer 2

The fraction of work that is left is

$\frac{8}{15}$

Given :-

Workdone by A = 15 days

Workdone by B = 20 days

To Find :-

If they work together for 4 days the amount of work left

Solution :-

Workdone by A is 15 days then ,

Workdone by A in oneday =

$\frac{1}{15}$

Workdone by B is 20 days then ,

Workdone by B in oneday = $\frac{1}{20}$

Workdone By A and B in oneday = $\frac{1}{15} + \frac{1}{20}$

$= \frac{20 + 15}{300} \\ = \frac{35}{300}$

Workdone by A and B in 1 day = $\frac{7}{60}$

Wordone by A and B in 4 days = $= 4 \times \frac{7}{60}$$= 1 \times \frac{7}{15} \\</p><p> = \frac{7}{15}$

Work left by A and B after Working for 4 days is $= 1 - \frac{7}{15} \\ = \frac{15 - 7}{15} \\ = \frac{8}{15}$