How do I solve the following combinations problem?
The sociology test has 15 true/false questions. In how many ways can you answer 11 correctly?
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A combination is when there is no repetition and order doesn't matter. The theorem is...
n! / r!(n-r)!
where n is the number of things to choose from (in this case true/false questions) and you choose r of them (in this case the questions that are answered correctly.
n = 15
r = 11
15! / 11!(15-11)!
15! / 11! * 4! = 1365
There are 1365 ways to answer 11 correctly.
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