The classes at the middle school want to raise money. the sixth grade runs a bake sale for 55 hours and makes $170$170. the seventh grade sets up a dunking booth for 44 hours and makes $112$112. the eighth grade has a car wash and makes $192$192 in 66 hours. which class has the highest rate for raising money?

The sixth grade makes 3.09 per hour

The seventh graders make 2.54 per hour

the eighth graders make 2.90 per hour

So the sixth graders make the most per hour. you can check this answer by taking the amount of money made and divide it by the time that it takes to raise the total amount of money raised by each class of students.