10C2

i know the answer is 45.

but for some reason, i can't get THAT answer. i keep getting something else....

anyone help me please?

thank you in advance!

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- Jan 25th 2009, 09:14 PMBig-KPermutations.
10C2

i know the answer is 45.

but for some reason, i can't get THAT answer. i keep getting something else....

anyone help me please?

thank you in advance! - Jan 25th 2009, 09:19 PMandreas
- Jan 25th 2009, 09:28 PMBig-K
But does this 10 C 2= http://www.mathhelpforum.com/math-he...5c678939-1.gif have anything to do with the 2nd step?

if it does, how?

thank you! - Jan 25th 2009, 09:44 PMandreas
well ,I assumed that you know this:

$\displaystyle 10!=10*9*8*7*6*5*4*3*2*1$

$\displaystyle 8!=8*7*6*5*4*3*2*1$

and $\displaystyle 2!=2*1$

Substituting this gives:

$\displaystyle \frac{10!}{8!2!} = \frac{10*9*8*7*6*5*4*3*2*1}{8*7*6*5*4*3*2*1*2*1} = \frac{9*10}{2}=45$