Max is painting a fence. The table shows the number of square feet he painted after various numbers of minutes. What is the rate of change?

Pick two lines on the table.

Each line has a number of minutes and a number of square feet.

Subtract the square feet of one line from the square feet of the other line.

This is the difference of square feet.

Now using the same two lines on the table, subtract the numbers of minutes in the same order you subtracted the square feet.

This is the difference of minutes.

Now divide the difference of square feet by the difference of minutes.

That is the rate of change in square feet per minute.