Question

A motor boat whose speed in still water is 16 km/hr. takes 2 hours more to go 80 km up stream than to return to the same point. Find The speed of the stream.

Answer 1

Answer:

(8√9 - 40) km/hr or approx. 3.08 km/hr.

Step-by-step explanation:

Let x be the rate of the water current.

(Time covered rowing upstream) - (Time covered rowing downstream) = 2

80/(16 - x) - 80/(16 + x) = 2

Solving for x,

80(16 + x - 16 + x) = 2(16 - x)(16 + x)

40(2x) = 256 - x²

80x = 256 - x²

x² + 80x + 1600 = 256 + 1600

(x + 40)² = 1856

x = -40 ± 8√29

We want x to be positive, so x = (8√29 - 40).

Therefore, the speed of the stream is (8√9 - 40) km/hr or approx. 3.08 km/hr.