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?

The boat travels upstream in 90 minutes = 3 miles

The boat travels upstream in 60 minutes = 3*60/90 miles

                                                         = 2 miles

Thus, Speed of Boat - Speed of Current = Upstream Speed of boat

or, Speed of Boat - 2 = 2

or, Speed of Boat = 2+2

or, Speed of Boat  = 4 miles/hour

Now,

Upon Returning,

The Boat travels Downstream,

Whereas,

Downstream speed of Boat = Speed of Boat + Speed of Current

                            &n