Previous Year Questions

Let the speed of boats A and B in still water are 6a km/h and 5a km/h respectively.

Let stream speed = s km/h

Upstream speed of boat A - upstream speed of boat B = 5

(6a - s) - (5a - s) = 5

a = 5

Then, speed of boat A in still water = 6 * 5 = 30 km/h

Speed of boat B in still water = 5 * 5 = 25 km/h

Now, time taken by boat A to cover 60 km upstream = time taken by boat B to cover 77.5 km downstream

60/(30 - s) = 77.5/(25 + s)

24(25 + s) = 31(30 - s)

600 + 24s = 930 - 31s

55s = 330

s = 6

From I:

Stream speed = s = 6 km/h

So, this statement is true.

From II:

Time taken by boat A to cover 108 km downstream = 108/(30 + s) = 108/(30 + 6) = 3 hours

So, this statement is true.

From III:

Downstream speed of boat B = 25 + s = 25 + 6 = 31 km/h ≠ 29 km/h

So, this statement is false.