ACT Preparation / Unit 10 ACT 0914 worked example, 60 to 90 seconds
Average Rate of Change From a Table
The idea
To find an average rate of change from a table or a graph, work in three steps. First, read the outputs at the two inputs that bound the interval. Second, subtract the outputs and the inputs in the same order. Third, divide, and attach units: output units per input unit.
In practice
Worked example: a town's population, in thousands, was 40 in 2010, 46 in 2014 and 58 in 2020. From 2010 to 2014: (46 − 40)/4 = 1.5 thousand per year. From 2014 to 2020: (58 − 46)/6 = 2 thousand per year. Over the whole span: (58 − 40)/10 = 1.8 thousand per year.
Where people slip
The rate over the whole span is not the average of the two smaller rates: (1.5 + 2)/2 is 1.75, not 1.8, because the intervals differ in length.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
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