Boats and Streams - General Aptitude

Q1:

What is the speed of the boat in still water?

I. The speed downstream is 12 kmph.

II. The speed upstream is 4 kmph.

III. In a to and fro journey between two points, the average speed of the boat was 6 kmph.

A I and II only

B All I, II and III

C III, and either I or II

D Any two of the three

E Any two of the three

ANS:D - Any two of the three

From I and II, speed of boat in still water =	1	(12 + 4) km/hr = 8 km/hr.
	2

From II and III, we get:

Using average speed =	2xy	, we get:	2 x 4 x y	= 6
	x + y		4 + y

8y = 24 + 6y

y = 12.

Required speed =	1	(12 + 4) km/hr = 8 km/hr.
	2

Similarly, I and III also give the answer.

Correct answer is (D).