A boat crossing a river...?

Question

A boat crossing a river which flows at 5m/s south heads directly across at 2m/s. If the river is 1km wide how long does the boat take to cross and how far downstream does it reach the opposite bank?

Answer 1

If the river is 1km wide that means it is 1000m wide. If it travels 2m/s a second that means it will take 500 seconds to get to the other side. The river is flowing at 5m/s, this means it will travel 2500m or 2.5km downstream in 500 seconds.