Question

A boat travels 8 hours downstream to cover a distance of 147.2 km while other boat travels 84.7 km in 11 hours upstream. Find the sum of speeds of both boats(in km/hr)

1. 25.2
2. 25.5
3. 25.7
4. 26.1
5. Cannot be determined.

Answer 1

Correct Answer - Option 4 : 26.1

Given:-

Distance by boat 1 in downstream in 8 hours = 147.2

Distance by boat 2 in upstream in 11 hours = 84.7

Formula:-

Speed = Distance/Time

Downstream speed = u + v

Upstream speed = u – v

u and v are boat and stream speeds.

Calculation:-

Downstream speed of boat 1 = 147.2/8 = 18.4 km/hr

Upstream speed of boat 2 = 84.7/11 = 7.7 km/hr

Hence,

b1 + b2 = b1 + v + b2 – v = 18.4 + 7.7 = 26.1 km/hr

Relative speed when boats are going in opposite direction is independent of stream speed.