Question

A works twice as that as B. If B can complete a work in 12 days independently, then the number of days in which A and B can together finish the work is

• A. 4 days
• B. 6 days
• C. 8 days
• D. 18 days

Answer 1

The correct option is A 4 days

A is twice as fast of B, A will take just $6$ days to the same work alone since $B$ takes $12$ days.
So, Amount of work done by A in one day $=\frac{1}{6}$
Amount of work done by B alone $=\frac{1}{12}$
Amount of work done by both of them in one day $=\frac{1}{6}+\frac{1}{12}=\frac{1}{4}$
Thus, number of days taken by both of them to do the work together $=\frac{1}{\frac{1}{4}}=4$