Problem 19 of 35alg-019
Lena drives 120 miles at 60 miles per hour, then another 120 miles at 40 miles per hour. How many hours does the whole trip take?
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Solution walkthrough1:31
- Draw the trip as two legs. Each leg is miles, but the speeds differ: and miles per hour.
- Distance speed time, so time distance speed. Use it on each leg separately.
- First leg: miles at miles per hour takes hours.
- Second leg: miles at miles per hour takes hours.
- Add the two times: hours for the whole trip.
- Traps: adds the two speeds, averages them, and uses miles per hour for the whole trip.