How to do this 10th grade level math problem

The cost of a 20 ounce box of cereal increased from 4.25 to 5.50 over 5 years. What is the annual rate of inflation?

Find the difference between 5.50 and 4.25 which is: $1.25. Then divide bY 5, which is .25 for each year the rate of inflation annually is 25 cents. Just a comment here, is this really 10th grade math? Because I'm
In eighth and this felt like a 4th grade problem to me.