1. 

What is the speed of the boat in still water ?

I. The boat covers a distance of 48 kms in 6 hours while running upstream.

II. The boat covers the same distance in 4 hours while running downstream.

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 E

Explanation:

 I. Speed upstream = 48 km/hr = 8 km/hr.
6

II. Speed downstream = 48 km/hr = 12 km/hr.
4

Speed of the boat = 1 (8 + 12) km/hr = 10 km/hr.
2

Thus, I and II together give the answer.

Correct answer is (E).