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Question

6 junior high classes will be chosen to participate in a school lunch survey. There are 23 junior high classes in the school. In how many ways can the classes be chosen?

Answer 1

The problem of selecting 6 classes from a total of 23 is a combination question because the order doesn't matter, just who is picked. That means you want to solve for

C(23,6) = 23! / (6! (23 - 6)!) = 23! / 6!17! = 100,947

meaning that there are 100,947 ways to choose the 6 classes for the survey

Answer 2

This is a combination problem; C(n,r).

 

In this question do you know what  n and r are and how to substitute in your formula for C(n,r)?