1. 

What is the speed of the boat in still water ?

I. It take 2 hours to cover the distance between A and B downstream.

II. It take 4 hours to cover the distance between A and B upstream.

A. I alone sufficient while II alone not sufficient to answer
B. II alone sufficient while I alone not sufficient to answer
C. Either I or II alone sufficient to answer
D. Both I and II are not sufficient to answer
E. Both I and II are necessary to answer

Answer: Option D

Explanation:

Let AB = x km.

 I. Speed downstream = x km/hr
2

II. Speed upstream = x km/hr.
4

Speed of boat in still water = 1 x + x km/hr.
2 2 4

Thus, I and II both even do not give the answer.

Correct answer is (D).