Homework Help: Math+ confused?!

Posted by Math on Tuesday, May 15, 2007 at 2:11pm.

I had to solve for this:

1) choose 4 people from a class of 12
My answer:
n=12 r=4
12C4 = 495

2) chosse 8 people from a class of 12
my answer:
n=12
r=8
12C8 = 495

why is it that they both eqaul 495? maybe I am doing it wrong but I am confused why do they both equal 495?

They are the same, both 2 from the mean of 6. If you do 12C6, you get the max. A neat thing to do is to graph each possibilty,
12C1
12C2
12C3 and so on until

12C12.

Graph number combinations vs n.

If you smooth it up, you get the binomial approximation to the normal probability curve.

thanks bobpursley

to go along with what bobpursley showed you, try to finish this pattern

1
1 1
1 2 1
1 3 3 1
1 4 6 4 1
1 5 10 10 5 1
...
.
.
to get a new number, add the one immediately above and one to the left, the left column is made up of 1's

This is Pascal's Triangle. Look at the row that starts with 1 12 ...
Did you notice something?

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