Question 327879
If a bicyclist rides at 10 miles per hour for 10 minutes, and then speeds up to 20 miles per hour for the next 20 minutes, what is her average speed for this ride? 
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Find the total distance, divide it by the total time.
10 mph*(10/60) + 20 mph*(20/60) = 500/60 miles
= 25/3 miles
Time = 1/2 hour
--> 50/3 mph
=~ 16.67 mph