A cyclist rides 36 km from town A to town B at a steady 18 km/h, then straight back at 12 km/h.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A cyclist rides from town A to town B at a steady , then straight back at . Find her average speed for the whole round trip.
Need a reminder? The key ideaShow
Speed distance time; velocity displacement time. Average speed total distance total time. .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Times. Going: . Coming back: .
Step 2. Average. .
Answer: .
Watch out. It is not , the mean of the two speeds: she spends longer at the slower speed.
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