# Simple probability question

• Dec 11th 2012, 08:58 AM
VII
Simple probability question
Hi There's a 15% chance to get a blue.

I've got 3 chances to hit blues. What's the chance I hit exactly 2/3 blues?
• Dec 11th 2012, 09:19 AM
Plato
Re: Simple probability question
Quote:

Originally Posted by VII
Hi There's a 15% chance to get a blue.
I've got 3 chances to hit blues. What's the chance I hit exactly 2/3 blues?

As written, it is too vague to answer.
• Dec 11th 2012, 09:28 AM
VII
Re: Simple probability question
There's some sweets in a bag. There's a 15% chance to get a blue sweet.
I will take a sweet out, and put it back in.
If take a sweet out and put it back 3 times, what's the chance 2/3 of those sweets will be blue?
• Dec 11th 2012, 09:36 AM
Plato
Re: Simple probability question
Quote:

Originally Posted by VII
There's some sweets in a bag. There's a 15% chance to get a blue sweet. I will take a sweet out, and put it back in.
If take a sweet out and put it back 3 times, what's the chance 2/3 of those sweets will be blue?

Simple binomial probability: $\binom{3}{2}(.15)^2(.85).$
• Dec 11th 2012, 09:52 AM
VII
Re: Simple probability question
I don't understand that >.>
What's the % chance of getting 2/3 blues?
• Dec 11th 2012, 11:30 AM
Plato
Re: Simple probability question
Quote:

Originally Posted by VII
I don't understand that >.>
What's the % chance of getting 2/3 blues?

If you do not understand how to evaluate a binomial coefficient, $\binom{N}{k}$ then you have no business trying this problem.