With no stops, it takes 3 hours for a motorist to make a trip driving at an average speed of 65 mph. When the motorist stops for gas and a sandwich on the same trip, he averages 60 mph. How many minutes long is the stop?
3 hours x 65 miles/hour = 195 miles
195 miles/60mph = 3.25 hours
Originally 3 hours now 3.25 hours .25 hours longer with stop .25 hr = 15 minutes.