Question

Sahil, rowing a boat and covers a distance of 96 km in 12 hours downstream. He covers (1/8)th of the distance in 4 hours when rowing upstream. Calculate the speed of the stream.
1. 1.5 km/h
2. 2.0 km/h
3. 2.5 km/h
4. 3.5 km/h

Answer 1

Correct Answer - Option 3 : 2.5 km/h

Given

Distance covers in downstream = 96 km

Time to cover downstream distance = 12 hours

Distance covers in upstream = (1/8) of 96

Time taken to cover upstream distance = 4 hours

Formula used

Speed = Distance/Time

Speed of stream = (Downstream speed - Upstream speed)/2

Calculation

Downstream speed(D_s) = 96/12

⇒ 8 km/h

Upstream speed(U_s) = [96 × (1/8)]/4

⇒ 12/4

⇒ 3 km/h

Speed of the stream = (8 - 3)/2

⇒ 5/2

⇒ 2.5 km/h

∴ Speed of stream is 2.5 km/h.