Question

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?

Answer 1

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