A boat travels upstream and after one hour has gone 10 km.The boat next travels downstream and after one hour has gone 14 km.If the boat's speed relative to the water is constant,what is the speed of the current in the river?
A)1 km/h
B)2 km/h
C)3 km/h
D)4 km/h

Question

Quizplus · Accepted Answer

Let's assume that the speed of the boat in still water is B km/h and the speed of the current is C km/h.

When the boat travels upstream, it is moving against the current which means its effective speed is B - C km/h.

So, we can write: distance = speed x time
10 = (B - C) x 1

Similarly, when the boat travels downstream, it is moving with the current which means its effective speed is B + C km/h.

So, we can write: distance = speed x time
14 = (B + C) x 1

We now have two equations and two unknowns (B and C).

Solving these equations, we get:

B = 12 km/h
C = 2 km/h

Therefore, the speed of the current in the river is 2 km/h, which is option B.

A Boat Travels Upstream and After One Hour Has Gone