Problema Solution
A man rowed 3 miles upstream in 90 minutes. If the river flowed with a current of 2 miles per hour, how long did the man's return trip take?
Answer provided by our tutors
Speed upstream = 3miles / 1.5 hours = 2mph
Let the river's speed be 'c', then c = 2mph
Let his rowing speed be 'r', then:
r = 2 + c = 2 + 2 = 4
He rowed at 4 mph upstream, so on the return trip if he still rows at 4mph he will move at 4+2=6 mph because he is rowing with the current.
3 / 6 = 0.5
At 6mph, the 3 mile return trip will take only .5 hours.