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
10C5, and some write it
.
But it means "The combinations of 10 things taken 5 at a time, and it
can be calculated
=
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