Question

A can do a piece of work in 80 days.He works at it for 10 days and then B alone finishes remaining work in 42 days. In how many days could both do it?

Answer 1

Now A can do a price of work in $80$ days. So let the total work $=80$units.

$A\to 80$ days$=1$ unit/day

So in $10$ days, A has completed $10$ units

$\therefore$ Remaining work$=70$ units

Now B finishes this in $42$ days. So rate of work if $B=\frac{70}{42}=\frac{5}{3}$ unit/day

Thus$=A+B=1+\frac{5}{3}$

$=\frac{8}{3}$

So time taken$=\frac{\frac{80}{8}}{3}=30$days.