Question

A does $\frac{4}{5}$ of a work in 20 days. After that, he calls B and they together finish the remaining work in 3 days. How long B alone would take to do the whole work?

• A. 23 days
• B. 37 days
• C.
• D. 40 days

Answer 1

The correct option is C

Whole work is done by A in $(20\times \frac{5}{4})=25days$

Now,$(1-\frac{4}{5})$ i.e. $\frac{1}{5}$ work is done by A and B in 3 days.

Whole work will be done by A and B in (3×5) = 15 days.

Let B can complete the work in x days.

$\frac{1}{25}+\frac{1}{x}=\frac{1}{30}$

$x=\frac{75}{2}$

$=37.5days$