Question

The distance between two cities is one hundred miles, and a woman drives from one city to the other at a rate of fifty mph. At what rate must she return if the total travel time is three hours and forty minutes?

45 mph
54 mph
60 mph

Answer 1

the answer is 60mph in order for her to travel for 3 hours and 40 minutes

Answer 2

It takes her (100 mi)/(50 mi/h) = 2 h to get to her destination. She has 1 h 40 min = 100 min for her 100 mi return trip.
.. (100 mi)/(100 min) = (60 mi)/(60 min) = 60 mi/h

She must return at the rate of 60 mph to complete the trip in 3 h 40 min.