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May 7, 2015

Posted by **Rena** on Tuesday, December 14, 2010 at 10:19pm.

- Math -
**Reiny**, Tuesday, December 14, 2010 at 10:40pmC(57,8) x C(43,4) = ....

- Math -
**Rena**, Tuesday, December 14, 2010 at 10:44pmIs the answer 2508.52

and if so, how do I explane the whole solution. I am acting as a elementary teacher and have to discuss how to work each part out.

- Math -
**Reiny**, Tuesday, December 14, 2010 at 11:04pmthe answer has to be a whole number, you can't have part of a committee, (although with most governments that is obviously possible)

C(n,r) or_{n}C_{r}

is defined as n!/(r!(n-r)!)

and gives us the number of combinations of r things from n possibilites

e.g. given A, B, C, D, how many combination of 2 letters can we form

-we could list them AB, AC, AD, BC, BD, and CD

-notice this would be C(4,2) = 4!/(2!2!)

= 4x3x2x1/(2x1x2x1) = 24/4 = 6

a number like C(57,8) is quite large

around 1.6 billion

and to do it on your calculator by just using the definition, will overload your calculator.

Look for a key labeled something like_{n}C_{r}

test it on C(4,2)

enter 4

press 2nd_{n}C_{r}

press 2

=

you should get 6

btw, the answer to your question is usually left in the notation I used, to express it in its full 15 digit number is rather futile.

Are you doing this in elementary school?? Wow

where?