Question

In how many ways can 2 singers be selected from 10 who came to audition?

Answer 1

10 for the first spot, and 9 left for the second spot = 10*9, or 10P2

Answer 2

45

Answer 3

or 10 "nCr" 2 = 45

Answer 4

good idea, wrong application i believe

Answer 5

this isnt a nCr, its an nPr

Answer 6

i don't understand how it's not 90, because that's what i did to. how do I knew when i can and cannot use that process amistre did?

Answer 7

know*

Answer 8

whenever you have to pick from a number of applicants, its P for "pick" in my eyes

Answer 9

whenever the order doesnt matter, then its groups that count. nCr for groupings

Answer 10

10 Pick 2 = 10P2 = 10*9 = 90

Answer 11

This should be \(\binom{10}{2} = 45 \)

Answer 12

Fair enough, I've never had to use P... Whenever I've done this in stats (ie with Binomial distribution) it's been nCr...

Answer 13

How does the order matter in this, isn't it just saying 2 singers?

Answer 14

i could be wrong, depends on how you interpret the question

Answer 15

if you have 2 people that are auditioning; then you need to pick 1 for the 1st and 1 for the 2nd

Answer 16

the answer is 45 i know that for sure, just trying to understand

Answer 17

joe then sally is a different order than sally then joe

Answer 18

oh okay

Answer 19

No, as there are many different ways of picking 2 people from a bag of 10, which is different from picking 10 from a bag of 2...

Answer 20

amistre,

>>In how many ways can 2 singers be selected from 10 who came to audition?


"selected" is the keyword here.

Answer 21

i can see that interpretation as well :)

Answer 22

But unfortunately 10P2 doesn't seem to be the correct interpretation here. :(

Answer 23

right, then if it aint 90, go 45 ;)

Answer 24

how do i put this into a calculator? its not 10!2 is it because that doesn't work

Answer 25

10P2/2!

Answer 26

the button that looks like nCr you would type 10 'nCr' 2

Answer 27

sooo

10!/2!(10-2)! perhaps?

Answer 28

which gives you an answer of 45.

Answer 29

or the factorial method, yes!

Answer 30

10*9*8*7*6*5*4*3*2
------------------
8*7*6*5*4*3*2*2

Answer 31

sorry i totally forgot how to do this. when i click permutations it puts in nPr() on the screen. where do i put the 10 and 2? and why is it 10 and 2 instead of 2 then 10?

Answer 32

It is 10C2 because 10 (n) is the number of values and 2 (c) is the number you are choosing.

Answer 33

I don't know how you would do it in that format, you know your calculator best.

Answer 34

so its combination or permutation?

Answer 35

ok its a combination because the order does not matter. i did this and got 45.

Answer 36

That's right.