Question 10

Level pending

Find the value of the expression.

9C2=?

note: nCr represents the number of combinations of n objects chosen r at a time.

Use the formula shown below to evaluate 9C2.

nCr= n ! r ! ( n − r ) ! \frac{n!}{r!(n-r)!}


The answer is 36.

Luye Xue by Luye Xue , 19, China

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1 solution

Luye Xue
Feb 24, 2015

nCr= n ! r ! ( n − r ) ! \frac{n!}{r!(n-r)!}

9C2= 9 ! 2 ! ( 7 ! ) \frac{9!}{2!(7!)}

9C2=36

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