Question

If A and B together can complete a piece of work in 15 days and B alone in 20 days, in how many days can A alone complete the work?
A.60
B.45
C.40
D.30

Answer 1

$\textbf{\huge{ANSWER:}}$

Given:

A and B can together can complete the work in = 15 days

B alone can complete the work in = 20 days

1 day work of A and B together = $\frac{1}{15}$ ...(1)

1 day work of B alone = $\frac{1}{20}$ ...(2)

(1) - (2)

$\frac{1}{15} - \frac{1}{20} \\ \\ = \frac{20 - 15}{300} \\ \\ = \frac{5}{300} \\ \\ = \frac{1}{60}$

Therefore, 1 day work of A alone = $\frac{1}{60}$

Total number of days required by A to complete the work alone = 60 days

Thus,

$\textbf{(A) 60 is the answer.}$

Hope it Helps!! :)