physics
posted by Tunde .
A boat is ravelling in a river with a current of 3 km/hr. The boat is capable of travelling at 10 km/hr in still water. How long will it take the boat to travel 7km upstream

The boat velocity relative to land, going upstream, is 10  3 = 7 km/h
Time to travel 7 km
= 7 km/(7 km/h)
= 1 hour