Question

While traveling downstream a boat cover 154 km in 7 hours. If the speed of the stream is 4 km/h then find the time taken by boat to cover the same distance upstream.

1. 11 hours
2. 13 hours
3. 9 hours
4. 12 hours
5. None of these

Answer 1

Correct Answer - Option 1 : 11 hours

Given:

Time take by boat to cover 154 km = 7 hours

Speed of stream = 4 km/h

Concept used:

Upstream speed = Downstream speed – (2 × speed of stream)

Calculation:

Downstream speed of the boat = 154/7

⇒ 22 km/h

Upstream speed of boat = 22 – (2 × 4)

⇒ 22 – 8

⇒ 14 km/h

Time is taken by boat to cover the same distance upstream = 154/14

⇒ 11 hours

∴ The time taken by boat to cover the same distance upstream is 11 hours.