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math- don’t know

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A club has 15 members and needs to choose 2 members to be co-presidents. In how many ways can the club choose its co-presidents?

Apr 28, 2019

#1
+491
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Since you are choosing 2 out of 15, you use the formula $$\frac{n!}{r!(n-r)!}$$, which is the combination formula

N represents number of items you are choosing out of, and r represents the number of items you are choosing.

Substituting in you will get 105 ways.

Whenever a problem is asking you to choose a certain number of items out of a total number of items, then use the formula above.

Apr 28, 2019
edited by CalculatorUser  Apr 28, 2019

#1
+491
+2

Since you are choosing 2 out of 15, you use the formula $$\frac{n!}{r!(n-r)!}$$, which is the combination formula

N represents number of items you are choosing out of, and r represents the number of items you are choosing.

Substituting in you will get 105 ways.

Whenever a problem is asking you to choose a certain number of items out of a total number of items, then use the formula above.

CalculatorUser Apr 28, 2019
edited by CalculatorUser  Apr 28, 2019