Question 815003
<pre>
There are 10 flips, flip#1, flip#2, ..., flip#9, and flip#10

"10 flips, choose 5" of those flips to be heads, and for each choice 
of 5 flips to be heads, you can choose the other 5 to be tails in
just 1 way,and that is to choose them all tails.

Some people write it C(10,5), some write it 10C5, some write it

<sub>10</sub>C<sub>5</sub>, and some write it {{{(matrix(2,1,10,5))}}}.

But it means "The combinations of 10 things taken 5 at a time, and it

can be calculated {{{10!/(5!5!)}}} = {{{(10*9*8*7*6*5*4*3*2*1)/((5*4*3*2*1)(5*4*3*2*1))}}} 

Cancel what will cancel and multiply the rest out and you'll get 252.

Or you can do it on your TI-83 or 84.

Press ON
Press CLEAR
Type in the number 10
Press MATH
Press the left arrow key
Press 3

You wiil see 10 nCr and a blinking cursor

Type in the number 5

You wiil see 10 nCr 5 and a blinking cursor

Press ENTER

You will see 252.


Edwin</pre>