Question

A can do a work in 10 days,B can do a work in 12 days,they can do a work with the help of c in 4 days .In how many days c alone can do?​

Answer 1

'a' does work in 10 days

'b' does same work in 12 days

Let c does the work in x days.

a,b and c does

$\frac{1}{10} +\frac{1}{12} +\frac{1}{x}$

work in one day

$\frac{1}{10} +\frac{1}{12} +\frac{1}{x}= \frac{22x+120}{120x}$

So a,b and c does the entire work in $\frac{120x}{22x+120}$ days

But a,b and c does entire work in 4 days.

So

$\frac{120x}{22x+120} = 4$

$120x = 88x+480$

$32x = 480$

$x = 15$

'c' can do the work alone in 15 days