let the distance to the store be x miles
time for first trip = x/20
time for second trip = x/30
total time = x/20 + x/30 = x/12
avg speed = total distance/total time
= 2x/(x/12)
= 2x(12/x) = 24 mph
You drive to the store at 20 mph and return by the same route at 30 mph. Ignoring the time spent at the store, what was your average speed?
1 answer
1 answer