It took Eric 8 hours to drive to a job interview. On the way home, he was able to increase his average speed by 18mph and make the return drive in only 5 hours. Find his average speed on the return drive.

Question

Rate x time =distance

Original drive- x. ____ _____
Return drive- ____ ____ _____

Answer 1

let the distance driven be x km
speed on first leg = x/8
speed on return leg = x/8 + 18 km/h
= (x + 144)/8 km/h

distance/rate = time
x/((x+144)/8) = 5
8x/(x+144) = 5
8x = 5x + 144
3x = 144
x = 48

so speed on return trip
= (48+144)/8 km/h
= 24 km/h