Question

The speed of a boat in still water is 9 km/hr and the speed of stream is 3 km/hr. The difference between the upstream speed and downstream speed will be:
1. 6 km/hr
2. 5 km/hr
3. 3.5 km/hr
4. 7.5 km/hr

Answer 1

Correct Answer - Option 1 : 6 km/hr

Given:

Speed of a boat in still water is 9 km/hr

Speed of the stream is 3 km/hr.

Concept Used:

Upstream Speed = Speed of boat - Speed of stream

Downstream Speed = Speed of boat + Speed of stream

Calculation:

Upstream Speed = Speed of boat - Speed of stream

⇒ Upstream Speed = 9 - 3

⇒ Upstream Speed = 6 km/hr

Downstream Speed = Speed of boat + Speed of stream

⇒ Downstream Speed = 9 + 3 

⇒ Downstream Speed = 12 km/hr

Difference between the upstream speed and downstream speed 

⇒ 12 - 6

⇒ 6 km/hr

∴ Difference between the upstream speed and downstream speed is 6km/hr.