The classes at the middle school want to raise money. The sixth grade runs a bake sale for 5 hours and makes $170. The seventh grade sets up a dunking booth for 4 hours and makes $112. The eighth grade has a car wash and makes $192 in 6 hours. Which class has the highest rate for raising money?

This is a multiple step question. Before you can answer it you must find what it is asking, which is the highest rate for making money, or the greatest rate of change. To compare the rate of change between each grade, you must first have them in common units, which can be done by finding how much money was made by each grade in one hour. To find this, divide the number of dollars made by the number of hours it was made in to get how much was made in one hour. Doing this shows that the sixth grade made 34 dollars an hour (170 divided by 5), seventh made 28 dollars an hour (112/4), and the eighth grade made 32 dollars an hour (192/6). Then compare the numbers to see that the greatest amount earned in one hour was 34 dollars, by the sixth grade, which then becomes your answer: The sixth grade had the highest rate for raising money.