BOATS and STREAMS Q81

81. A boat takes a total time of three hours to travel downstream from P and Q and upstream back from Q to P. What is the speed of the boat in still water?

I.The speed of the river current is 1 km per hour.

 II. The distance between P and Q is 4 km.

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 of the current = 1 km/hr.

II. PQ = 4 km.

Let the speed of the boat in still water be x km/hr. Then,

4	+	4	= 3. This gives x.
(x + 1)		(x - 1)

 Correct answer is (E).