Question

A and B together can do a piece of work in $6\frac{2}{3}$ days; but B alone can do it in 10 days. How long will A take to do it alone?

Answer 1

A and B can do the work in $=6\frac{2}{3}$ days
$=\frac{20}{3}$ days
B can do the work $=\frac{3}{20}$
$\therefore$ (A+B)'s 1 day work $=\frac{3}{20}$
B's 1 day work $=\frac{1}{10}$
A's 1 day work $=\frac{3}{20}-\frac{1}{10}$
$=\frac{3-2}{20}=\frac{1}{20}$
$\therefore$ A can do the work in = 20 days.