Question: There are 13 3-year-olds, 20 4-year-olds, 15 5-year-olds, and 22 six-year-olds at a particular Sunday school. If the 3 and 4-year-olds are in one class and the 5 and 6-year-olds are in another class, what is the average class size? Think carefully first, then make a decision:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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First find the total number of 3 - and 4 - year - olds: 13 kids + 20 kids = 33 kids. Then find the total number of 5 - and 6 - year - olds: 15 kids + 22 kids = 37 kids. Then add the two class sizes: 33 kids + 37 kids = 70 kids. Then divide the number of kids by the number of classes to find the average class size: 70 kids / 2 classes = 35 kids / class. So the answer is 35.