Question

a woman drives to work and averages 70 kilometers per hour for the trip. On her trip from work to home she averages 100 kilometers per hour. What is her average speed for the round trip?
average speed = total distance/total time

we don't know how far it is to her place of work,
let that distance be x

time on first part = x/70
time for return trip = x/100
total time = x/70 + x/100
= 17x/700

avg speed = 2x/(17x/700)
= 2x(700/17x)
= 1400/17 km/h
or appr 82.4 km/h

Related Questions

Rosea drives her car 30 kilometers to the train station, where she boards a train to complete her tr... Andrea made a car trip of 440 Kilometers. She averaged 54 Kilometers per hour for the frst part of t... Two hikers start out on the Kilimanjaro Trail at the same time and walk in the same direction. If on...