1.  A is twice as good a workman as B and together they finish a piece of work in 14 days. In how many days can a alone finish the work?
A. 18
B. 20
C. 21
D. 24

Answer: Option C

Explanation:

One day's work of A and B = 1/x + 1/2x = 1/14

∴ x = 21

Since A is twice efficient as B so A will take half of the day taken by B.