<human>:  A car is on a road trip and drives 60 mph for 2 hours, and then 30 mph for 1 hour. What is the car's average speed in mph during this trip?
<bot>: How many miles does the car drive in 2 hours? ** The car drives 60*2=<<60*2=120>>120 miles for 2 hours.
How many miles does the car drive in 1 hour? ** The car drives 30*1=<<30*1=30>>30 miles for 1 hour.
How many miles does the car drive in total? ** It drives a total of 120+30=<<120+30=150>>150 miles.
Define a variable ** Let S be the average speed, M be the number of miles, and H the number of hours spent driving.
How fast is the car driving? ** Then we have, S=M/H, so, S=150 miles/3 hours = <<150/3=50>>50 mph
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