Question

http://answers.yahoo.com/question/index?qid=20100522174649AAlPUoL

Why Does this person say this as an answer "When exactly one of these three is bad: there are 2 ways to pick the bad part and 10C2 = 45 ways to pick good parts. 2*45/220 = 9/22 "

Answer 1

ANY1??????????????????

Answer 2

because there are two bad parts, you choose one. So (2C1) = 2

Answer 3

and there are 10 good parts. You choose 2. (10C2)

(2C1) (10C2) / (12C3) = 9/22

Answer 4

Are you still there?

Answer 5

??

Answer 6

Why is it 10C2 though? can you maybe draw it to help me? I am confused with this question it is killing me

Answer 7

2 bad parts and 10 good parts yes?

Answer 8

yes

Answer 9

you select 3. But Only one of them is the bad one.

Answer 10

meaning the other 2 must be the good one

Answer 11

3 of the 12

Answer 12

what do you mean by 3 of the 12?

Answer 13

aren't there 12 parts. and you must pick 1 of 3 where 2 is good and 1 is bad

Answer 14

why do we cut it down individually saying 2C1 and 2C10?

Answer 15

10C2

Answer 16

because 1 of the bad parts can go with the other 2 good parts

and the other bad parts can also go with the 2 good parts

Answer 17

so is it saying that out of the 10 good parts we will have 2 that are good so we have to find the probability of those that are good of the good parts?

Answer 18

that will combine with 1 of the 2 bad parts

Answer 19

yes

Answer 20

But if 45 is the number of good parts like the answer says, why multiply by 2?

Answer 21

hold on, typo

Answer 22

ok

Answer 23

hold typo again

Answer 24

lol

Answer 25

suppose there are 2 bad parts, A and B, and 2 good parts, C and D. If you were to pick two and only one is bad, then from you have (2C1) * (2C1) = 4
AC
AD
BC
BD

it's the same analogy to the question. but this time you have 10 good parts. If you choose 2, you'll have 45 possible pairs

it's like
A with those 45 pairs
B with those 45 pairs

so you have 90 pairs total. Which is precisely (2C1) (10C2) = 2 * 45 = 90

Answer 26

ok

Answer 27

what are the 2C1 representing here? what exactly? This is my first statistics so this is all new for me sorry Ive never dealt with these questions before

Answer 28

2C1 means (2 choose 1), which is 2.

If you have 2 things, and you can choose 1 of them. You have 2 ways of choosing.