How much time does the man take in driving to and from the shopping center?

A man drives from his home at 30 miles per hour to the shopping center which is 20 miles from his home. On the return trip he encounters heavy traffic and averages 12 miles per hour. How much time does the man take in driving to and from the shopping center?

MetroEye: The average speed = \(\dfrac{Distance travelled}{Time Taken}\)

Time taken for the to-travel = \(\dfrac{20 miles}{30 miles per hour}\)

Time taken for the from-travel = \(\dfrac{20 miles}{12 miles per hour}\)

Total time = \(\dfrac{20}{30}\) + \(\dfrac{20}{12}\) = \(\dfrac{2}{3}\) + \(\dfrac{5}{3}\) = \(\dfrac{7}{3}\) hours = \(\dfrac{7}{3}\) * 60 = 140 minutes = 2 hour 20 minutes

The man took 2 hours 20 minutes in driving to and from the shopping center.