Exercise 12 Page 151

We in-line skate from an elevation of 720 feet to an elevation of 750 feet in 30 minutes, while our friend in-line skates from an elevation of 600 feet to an elevation of 690 feet in one hour. We want to compare the rates of change of elevation. To do so, remember that the rate of change is a ratio used to compare how a variable changes in relation to another variable. Rate of Change= Change iny/Change in x In our case, the change in y represents the change of the elevation and the change in x indicates the change in time. Rate of Change= Change of Elevation/Change in Time Let's start with our rate of change. The change of elevation will be the difference between 750 and 720 feet. Consider that the initial time is equal to 0 minutes, so the change in time will be equal to the difference between 30 and 0.

Now, we will calculate our friend's rate of change. This time the change in elevation will be the difference between 690 and 600. Since 1 hour is equal to 60 minutes, the change in time will be the difference between 60 and 0.

This means that the rate of change our friend has is greater than our rate of change.