posted by Anonymous .
A hunter wishes to cross a river that is 2.0 km wide and that flows with a speed of 5.1 km/h. The hunter uses a small powerboat that moves at a maximum speed of 12.3 km/h with respect to the water. What is the minimum time necessary for crossing?
Does it matter which portion of the opposite shore he arrives at?
It makes a difference. Aiming across the shore while drifting downstream is the quickest way to cross, and takes
2.0/12.3 = 0.1626 h = 9.76 minutes