Question 133086
20 miles per gallon is the same as {{{1/20}}} gallon per mile.  So the truck uses 1/20 of a gallon of gas per mile driven at 50 miles per hour.  At 60 miles per hour, the truck uses 30% more gas, or {{{1.3/20}}} gallons per mile.  {{{1.3/20=.065}}}, so for a 160 mile trip at 60 miles per hour, the truck would use {{{.065*160=10.4}}} gallons of gas.  Since the truck has a 10 gallon tank, it would have to stop for gas once during the trip.


Without stopping, the trip would take {{{t=d/r=160/60=8/3}}} hours.  But since it had to stop once for 20 minutes, or 1/3 hour, the entire trip would take {{{8/3+1/3=9/3=3}}} hours.