Question

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 the above 

c) III and either I or II 

d) data inadequate 

e) none of these

Answer 1

Correct option: d) data inadequate

Explanation:

From I and II, speed of boat in still water=1/2*(12+4)kmph =8 kmph from II and III we get: using average speed= 2xy/(x+y), wwe get: (2*4*y)/(4+y) =6 therefore 8y=24+6y and it gives y=12 required speed=1/2*(12+4)kmph =8 kmph.

Similarly i and III also give the answer. Therefore Correct answer is d