Question

A and B, working together can complete a job in 3 hours. If A alone can do the job in $7\frac{1}{2}$ hours, in how much time can B alone finish the job ?

Answer 1

A and B can together complete the job in 3 hours.

A alone can do in $\frac{15}{2}$ hours.

Let B can do in $x$ hours.

Then,

$\frac{1}{x}+\frac{2}{15}=\frac{1}{3}$

$\frac{1}{x}=\frac{1}{3}-\frac{2}{15}$

$\frac{1}{x}=\frac{3}{15}$

$x=5$

Hence, B alone can complete the jon in 5 hours.