1. 

If both the pipes are opened, how many hours will be taken to fill the tank?

I. The capacity of the tank is 400 litres.

II. The pipe A fills the tank in 4 hours.

III. The pipe B fills the tank in 6 hours.
A. Only I and II
B. Only II and III
C. All I, II and III
D. Any two of the three
E. Even with all the three statements, answer cannot be given.

Answer: Option B

Explanation:

II. Part of the tank filled by A in 1 hour = 1
4

III. Part of the tank filled by B in 1 hour = 1
6

(A + B)'s 1 hour's work = 1 + 1 = 5
4 6 12

A and B will fill the tank in 12 hrs = 2 hrs 24 min.
5

So, II and III are needed.

Correct answer is (B).