Need Help! Its a combination problem.5

- anonymous

Need Help! Its a combination problem.5

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- FireKat97

I don't think your factorial equation is right... follow this format \[\frac{ n! }{ k! (n-k)! }\]
and try simplifying now

- anonymous

15! / 15! (5-15)!

- anonymous

On my notes it says
nCk = n!/(n-k)! k!
so id rather do it that way :)
but it would still be the same way right?

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## More answers

- FireKat97

Wait actually

- anonymous

I wrote the wrong number..
I just need to figure out how to simplify 15C5

- anonymous

its supposed to be 3003 but idk how?
I can do it from a calculator, but on a quiz i need to be able to show my work

- FireKat97

You would get 15!/ 15!. -10! that way
and I don't think you should have a negative factorial

- anonymous

I got 15!/10! 5!

- FireKat97

yup thats right

- anonymous

|dw:1442908599294:dw|

- anonymous

The way i simplified it was
15 14 13 12 11 10
_________________________
10 5 4 3 2 1
I crossed out the 10's
and then from there it doesnt seem right, but its the way my teacher taught us.
so for ex, 5 *3 = 15 7*2 = 14

- anonymous

so then 3 would go on top of the 15
and the 7 would go on top of the 14

- FireKat97

yeah I did the same, then you can cancel a few other things out as well

- FireKat97

yup seems right so far

- anonymous

thats where im stuck because i cant get 3003
if i do then it would be 3 * 7 * 11 *13
but what happens to the 12?

- FireKat97

so answer is 3003 right?

- anonymous

yes

- FireKat97

okay so you have \[\frac{ 15 . 14. 13. 12. 11 }{ 5. 4. 3. 2. 1}\]

- anonymous

yes

- FireKat97

|dw:1442908920946:dw|

- FireKat97

do you follow what I did there?

- anonymous

is that a 4?

- anonymous

above the 12?

- FireKat97

yea

- anonymous

okay yeah i understand so far

- FireKat97

and it cancels with the 4 below

- FireKat97

yup so now we have left 3 x 7 x 13 x 11

- anonymous

OHH LOL OKAY I GET IT NOW ! AHHHH okay i was doing it right then

- FireKat97

yup you were right all along ahahahha :D

- anonymous

wait what happend to the 3? Lol

- FireKat97

the bottom one got cancelled to make the 12 on top into a 4

- anonymous

ooookay yay! thanks :)

- FireKat97

haha no problem :)

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