Q:

A) 30 | B) 40 |

C) 50 | D) 60 |

Answer: B) 40

Explanation:

Explanation:

(A+B)'s 15 days work = $\left(\frac{1}{20}\times 15\right)=\frac{3}{4}$

Remaining work = 1/4

Now, 1/4 work is done by A in 10 days.

Whole work will be done by A in (10 x 4) = 40 days.