Tara's car accelerated from 10 miles per hour to 70 miles per hour in 12 seconds. what is the approximate rate of change in the miles per hour that tara's car accelerated?
5m per hour per sec
8m per hour per sec
18m per hour per sec
48m per hour per sec

To find the rate of change you need to divide the number of miles she sped up per hour over the number of seconds. 
To find the number of miles she sped up per hour just subtract
70-10 = 60

Then divide:
60/12 = 5

The answer is 5m per hour per sec.

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