A boat covers a distance of 80 km downstream in 8 h while it takes 10 h to cover the same distance upstream. What is the speed (in km/h) of the boat in still water?

Correct option is C

Given:

Distance covered downstream = 80 km
Time taken downstream = 8 hours
Distance covered upstream = 80 km
Time taken upstream = 10 hours

Concept Used:

The speed of the boat in still water can be found using the formula:
Speed of boat in still water = (Downstream speed + Upstream speed) / 2
Where:
- Downstream speed = Distance / Time taken downstream
- Upstream speed = Distance / Time taken upstream

Solution:

Downstream speed = 80 km / 8 hours = 10 km/h
Upstream speed = 80 km / 10 hours = 8 km/h
Speed of boat in still water = (10 km/h + 8 km/h) / 2 = 9 km/h
Therefore, the speed of the boat in still water is 9 km/h.