Finite Math Examples

${}_{13}C_{6}$

Step 1

Evaluate

${}_{13}C_{6}$ using the formula

${}_{n}C_{r} = \frac{n!}{(n - r)! r!}$ .

$\frac{13!}{(13 - 6)! 6!}$

Step 2

Subtract

$6$ from

$13$ .

$\frac{13!}{(7)! 6!}$

Step 3

Simplify

$\frac{13!}{(7)! 6!}$ .

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Step 3.1

Rewrite

$13!$ as

$13 \cdot 12 \cdot 11 \cdot 10 \cdot 9 \cdot 8 \cdot 7!$ .

$\frac{13 \cdot 12 \cdot 11 \cdot 10 \cdot 9 \cdot 8 \cdot 7!}{(7)! 6!}$

Step 3.2

Cancel the common factor of

$7!$ .

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Step 3.2.1

Cancel the common factor.

$\frac{13 \cdot 12 \cdot 11 \cdot 10 \cdot 9 \cdot 8 \cdot 7!}{(7)! 6!}$

Step 3.2.2

Rewrite the expression.

$\frac{13 \cdot 12 \cdot 11 \cdot 10 \cdot 9 \cdot 8}{6!}$

Step 3.3

Simplify the numerator.

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Step 3.3.1

Multiply

$13$ by

$12$ .

$\frac{156 \cdot 11 \cdot 10 \cdot 9 \cdot 8}{6!}$

Step 3.3.2

Multiply

$156$ by

$11$ .

$\frac{1716 \cdot 10 \cdot 9 \cdot 8}{6!}$

Step 3.3.3

Multiply

$1716$ by

$10$ .

$\frac{17160 \cdot 9 \cdot 8}{6!}$

Step 3.3.4

Multiply

$17160$ by

$9$ .

$\frac{154440 \cdot 8}{6!}$

Step 3.3.5

Multiply

$154440$ by

$8$ .

$\frac{1235520}{6!}$

Step 3.4

Simplify the denominator.

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Step 3.4.1

Expand

$6!$ to

$6 \cdot 5 \cdot 4 \cdot 3 \cdot 2 \cdot 1$ .

$\frac{1235520}{6 \cdot 5 \cdot 4 \cdot 3 \cdot 2 \cdot 1}$

Step 3.4.2

Multiply

$6 \cdot 5 \cdot 4 \cdot 3 \cdot 2 \cdot 1$ .

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Step 3.4.2.1

Multiply

$6$ by

$5$ .

$\frac{1235520}{30 \cdot 4 \cdot 3 \cdot 2 \cdot 1}$

Step 3.4.2.2

Multiply

$30$ by

$4$ .

$\frac{1235520}{120 \cdot 3 \cdot 2 \cdot 1}$

Step 3.4.2.3

Multiply

$120$ by

$3$ .

$\frac{1235520}{360 \cdot 2 \cdot 1}$

Step 3.4.2.4

Multiply

$360$ by

$2$ .

$\frac{1235520}{720 \cdot 1}$

Step 3.4.2.5

Multiply

$720$ by

$1$ .

$\frac{1235520}{720}$

Step 3.5

Divide

$1235520$ by

$720$ .

$1716$