The average rate of change

Question

The amount of international phone calls in a certain country rose from

45 billion minutes in 1992, to 58.7 billion minutes in 1995.

Assuming a linear​ relationship, what is the average rate of change for this time​ period?

Answer 1

Average rate of change is the same as the slope of the line formed from the two points they have given. That's the (y₂ - y₁)/(x₂ - x₁) thing. So subtract the two minute values, subtract the two year values, and divide.