1. 

What is the speed of stream ?

I. The boat covers 24 km in 6 hours moving upstream.

II. The boat covers 24 km in 3 hours moving downstream.

III. The ratio between the speed of boat and stream is 3 : 1 respectively.
A. Any two of the three
B. I and II only
C. II and III only
D. I and III only
E. All I, II and III

Answer: Option A

Explanation:

I. Speed upstream = 24/6 km/hr = 4 km/hr.

II. Speed downstream = 24/3 km/hr = 8 km/hr.

III. Let the speed of the boat in still water be 3X km/hr.

Then, speed of the stream is X km/hr.

∴ Speed downstream = 2X km/hr,

Speed upstream = X km/hr.

From I and II, we get speed of stream

= 1 (8 - 4) km/hr
2

= 2 km/hr.

From II and III , we get 2X = 8

<=> X = 4

Speed downstream = 8 km/hr.

∴ Speed of stream = 1 (8 - 4) km/hr
2

= 2 km/hr.

From I and III, we get X = 4 and 2X = 8.

∴ Speed of stream = 1 (8 - 4) km/hr
2

= 2 km/hr.

Thus, any two of the three will give the answer.

∴ Correct answer is (A)