Question

Please help?!
Lisa can choose 4 of her 9 friends to come with her family on a camping trip. How many ways can she choose the friends that come with her?
a. 126

b. 756

c. 3024

d. 6561
I think it is either a. 126 or c. 3024... is it something else? or what is the answer? I am confused. :/

Answer 1

I know this one :D

Answer 2

It'd be 9choose4 aka 9c4

Answer 3

Can you please explain it to me too? I don't get it haha

Answer 4

nCr = n!/[(n - r)! * r!]

Answer 5

What does that mean? haha :P

Answer 6

Lol

Answer 7

yeah lol is right! haha I do not get these at all! lol (see what i did there?!) teepee

Answer 8

***teeheeee lol not teepee.. auto correct is not on my side! haha

Answer 9

9c4 =

\(\Large \color{Black}{\Rightarrow {9! \over (9 - 4)! \times 4!} }\)

\(\Large \color{Black}{\Rightarrow {9! \over 5! \times 4!} }\)

\(\Large \color{Black}{\Rightarrow {9 \times 8 \times 7 \times 6 \over 4 \times 3 \times 2} }\)

Answer 10

Lol teepee

Answer 11

\(\Large \color{Black}{\Rightarrow {3024 \over 24} }\)

\(\Large \color{Black}{\Rightarrow 126 }\)

Answer 12

yeah hahaha :P Why do you stop at 6 though??

Answer 13

I've cancelled 5!

Answer 14

So the answer is a. 126 then? @ParthKohli ??

Answer 15

oh and i see what you did there. I get it now haha.... @ParthKohli so the answer is 126 ways???

Answer 16

Yes

Answer 17

:P

Answer 18

Do you have a scientific calculator?

Answer 19

yes, but i do not know how to use it :P

Answer 20

Use this site then, for example I've entered one already for you http://www.wolframalpha.com/input/?i=9c4

Answer 21

oh wait no! i don't have one... haha nvm lol it's just a regular calculator! lol my bad

Answer 22

:P

Answer 23

Thanks for the link! It will be very useful! So is that a scientific calculator? ONe that is really easy to use right? teehee

Answer 24

It's more than a scientific calculator! It has all subjects!

Answer 25

OMG! it does! Wow! Once summer break starts, I'm gonna learn how to use it! or better yet, memorize how to use the entire thing!!! :) THanks for the link @ParthKohli and thanks for the help!

Answer 26

No it automatically understands what you are trying to say!

Answer 27

wow! THanks! ;) that's one handy dandy tool! how'd u find out about it?

Answer 28

If you enter 9c4 or 9choose4 or 9 choose 4 or anything, it'll understand. It's very smart.

Answer 29

It's famous all over the world. You didn't know?

Answer 30

no i didn't haha really? it is? I had noooo idea lol

Answer 31

thanks!! :) for the link AND the help!