Math
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?
asked by
Justin

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
posted by Reiny
Respond to this Question
Similar Questions

Algebra
You commute 56 miles one way to work. The trip to work takes 10 minutes longer than the trip home. Your average speed on the trip home is 8 miles per hour faster. What is your average speed on the trip home? I don't understand why 
MATH
Andrea made a car trip of 440 Kilometers. She averaged 54 Kilometers per hour for the frst part of the trip and 80 kilometers per hour for the secound part. If the total trip took 6 hours, how long was she traveling at 80 
math
Andrea made a car trip of 440 Kilometers. She averaged 54 Kilometers per hour for the frst part of the trip and 80 kilometers per hour for the secound part. If the total trip took 6 hours, how long was she traveling at 80 
Math
can you help i dnt know what to do so could you tell me how to solve it 1. every weekend, Phil drives from his home to his favorite amusement park, a distance of 60 miles. a. If he averages 40 mph for the first half of the trip, 
math
Phil is making a 40kilometer canoe trip. If he travels at 30 kilometers per hour for the first 10 kilometers, and then at 15 kilometers per hour for the rest of the trip, how many minutes more will it take him then if he travels 
math
Phil is making a 40kilometer canoe trip. If he travels at 30 kilometers per hour for the first 10 kilometers, and then at 15 kilometers per hour for the rest of the trip, how many minutes more will it take him then if he travels 
math
Phil is making a 40kilometer canoe trip. If he travels at 30 kilometers per hour for the first 10 kilometers, and then at 15 kilometers per hour for the rest of the trip, how many minutes more will it take him then if he travels 
math
Phil is making a 40kilometer canoe trip. If he travels at 30 kilometers per hour for the first 10 kilometers, and then at 15 kilometers per hour for the rest of the trip, how many minutes more will it take him then if he travels 
Precalculus
Rosea drives her car 30 kilometers to the train station, where she boards a train to complete her trip. The total trip is 120 kilometers. The average speed of the train is 20 kilometers per hour faster than that of the car. At 
physics
a woman drives at a speed of 20m/s for part of a trip and at a speed of 30m/s for the rest of the trip if she spends 10 minutes driving at each speed determine her average speed for the full trip. If instead she drives 10