Today we are going to review finding the AVERAGE RATE OF CHANGE. The average rate of change is also called the slope. To find the average rate of change we find the difference of the y-values divided by the difference of the x-values.

Let's look at the growth of a dolphin. If a dolphin weighed 350 pounds when he was born and grew to be 800 pounds five years later, what was the dolphin's average rate of change?

We could write the information as points.

Remember, the x-values are the independent values. This is frequently the time. In this case the x-values will be the age of the dolphin.

Since the weight of the dolphin depends on the age, this is our dependent variable. So, weight will be our y-values.

When the dolphin was born, he weighed 350 pounds.

This is the point (0, 350)

When the dolphin was 5 years old, he weighed 800 pounds.

This is the point (5, 800)

Step 1 - Find the difference in y-values

800 lbs - 350 lbs = 450 pounds

Step 2 - Find the difference in x-values

5 yrs - 0 yrs = 5 years

Step 3 - Divide the difference in y-values by the difference in x-values

450 lbs / 5 yrs = 90 lbs/yr

This means the dolphin's average weight of change was an increase of 90 pounds every year

Now it is time to try a Released EOC question

Try the problem on your own before you check your answer! You can review pages 4 and 5 if you need help.

I know you can do it!

Let's see how you did!

Since it says from week 8 to week 12, we want to use the points (8, 0.04) and (12, 0.49)

Step 1 - Find the difference in y-values

0.49 oz - 0.04 oz = 0.45 ounces

Step 2 - Find the difference in x-values

12 wks - 8 wks = 4 weeks

Step 3 - Divide the difference in y-values by the difference in x-values

0.45 oz / 4 wks = 0.1125 oz/wk

The plankton grew 0.1125 ounce per week