Question

Downstream distance of boat 1 in 5 hours is 35 km while downstream distance of boat 2 in 4 hours is 52 km. Ratio of speeds of boats in still water is 2 ∶ 5, find speed of stream(in km/hr).

1. 1
2. 1.5
3. 2
4. 2.5
5. 3

Answer 1

Correct Answer - Option 5 : 3

Given:-

Downstream distance of boat 1 in 5 hours = 35 hours.

Downstream distance of boat 2 in 4 hours = 52 hours.

Ratio of boat speed = 2 ∶ 5

Formula:-

Speed = Distance/Time

Downstream speed = u + v

u and v are boat and stream speeds.

Calculation:-

Downstream speed of boat 1 = 35/5 = 7 km/hr

Downstream speed of boat 2 = 52/4 = 13 km/hr

Let speed of boats in still water be 2x and 5x respectively.

2x + v = 7

5x + v = 13

Solving both we get, x = 2 and v = 3