Question

A works twice as fast as B. If B can complete a work in 24 days independently, the number of days in which A and B can together finish the work is?

• A. 12 days
• B. 9 days
• C. 8 days
• D. 6 days

Answer 1

The correct option is C

8 days

Given that B can complete the work in 24 days.

Hence B's one day work = $\frac{1}{24}$

Since A is twice as efficient as B, so A's one day work $=2\times \frac{1}{24}=\frac{1}{12}$
The work completed by A and B in one day $=\frac{1}{24}+\frac{1}{12}=\frac{1+2}{24}=\frac{3}{24}=\frac{1}{8}$

Hence they can finish $\frac{1}{8}$ work in one day.

$\therefore$ A and B can together finish the work in 8 days.