Oreos

[dylanthewidge]

This should be simple but my 4 other people got a different answer than me.

You have a bag with 6 oreos. 4 are vanilla, and 2 are chocolate. You randomly pick 2 oreos from the bag.

Q: "What is the probability that the 2nd oreo is chocolate."


Since the prob that the 1st oreo is chocolate is 1/3, wouldn't the prob that the 2nd oreo is chocolate also be 1/3?



The 2 ways to get chocolate 2nd are "cc" and "vc", which I did below:

(2/6)(1/5) + (4/6)(2/5) = (2/30) + (8/30) = 1/3



Thanks
Hope this makes sense

[Mean Joe]

Looks good.

Your method also can calculate probability that 2nd oreo is vanilla: "cv" or "vv"
(2/6)(4/5) + (4/6)(3/5) = 2/3
That complements your answer for chocolate.

You can ask your other people to do their calculations for "2nd oreo is vanilla" and see if their answers are complementary.

[Dason]

I was disappointed that this thread wasn't just a discussion about how delicious oreos are.

[BGM]

Since you have no knowledge about the other picks, the "order" of picks is irrelevant.

i.e. The probability of 1st/2nd/.../nth oreos is chocolate is the same. It is simply 2/6.