Question

Two ribbons are selected at random from a container holding 5 purple and 6 white ribbons. Find the probability that both ribbons are white.

Answer 1

First you need the total number of ribbons. The probability of getting two ribbons (this time will be without replacement) will be

P(1st ribbon)*P(2nd ribbon)

P(1st ribbon) is just the number of white ribbons, over the total.

P(2nd ribbon) is the number of remaining white ribbons, over the remaining total ribbons.

Answer 2

6/11
& 5/11 ?
or is this assuming that I'm removing both white ribbons?
(Sorry, I make math more complicated for myself by over thinking everything.)

Answer 3

Wait, >.<
6/11
then ... 5/10 = 1/2 ?
(See what I mean. )

Answer 4

haha, excellent. You found your mistake and corrected yourself! :)

Answer 5

Now you just need:

P(1st ribbon)*P(2nd ribbon)

Answer 6

Do I just multiply them? Or, am I thinking incorrectly again? lol.

Answer 7

Don't doubt yourself, you're correct.

You can also use combinations here, if you've done those:

from 6 white ribbons, choose 2, over from 11 total ribbons choose 2.
\[\Large \frac{ 6C2 }{ 11C2 }\]

Answer 8

I'm not sure what to do with that equation, I haven't worked with them.

Answer 9

Never mind it then :)

Answer 10

Just use P(1st ribbon)*P(2nd ribbon)

Answer 11

6/11*1/2

Answer 12

or 3/11 :)

Answer 13

Yes :)