Problem Solving (PS) | Re: A cyclist travels 20 miles at a speed of 15 miles per hour.

We know that distance/rate = time. If we let the speed of the return trip = r, then our equation for the time for the entire trip is:

time going + time returning = 2 hours

20/15 + 20/r = 2

4/3 + 20/r = 2

Multiplying by 3r, we have:

4r + 60 = 6r

60 = 2r

30 = r

Answer: D
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