My Math Forum permutation and combination (1)

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 June 7th, 2012, 01:06 PM #1 Newbie   Joined: May 2012 Posts: 9 Thanks: 0 permutation and combination (1) 5 bottle of spoiled milk mixed with 15 bottle of good milk 1-if 3 bottle were selected at random, whit is the probability that they contain unspoiled milk 2-probability that the three selected at random are spoiled milk
June 7th, 2012, 01:26 PM   #2
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Re: permutation and combination

Hello, talo0000!

Quote:
 5 bottles of sour milk is mixed with 15 bottles of good milk. 1. If 3 bottle were selected at random, what is the probability that they contain good milk?

$\text{There are: }\:{15\choose3} \,=\,455\text{ ways to select 3 good bottles.}
\text{There are: }\:{20\choose3} \,=\,1140\text{ ways to select any 3 bottles.}$

$\text{Therefore: }\:P(\text{3 good}) \;=\;\frac{455}{1140} \;=\;\frac{91}{228}$

Quote:
 2. What is the probability that the three selected at random are sour milk?

$\text{There are: }\:{5\choose3} \,=\,10\text{ ways to select 3 sour bottles.}
\text{There are: }\:{20\choose3} \,=\,1140\text{ ways to select any 3 bottles.}$

$\text{Therefore: }\:P(\text{3 sour}) \;=\;\frac{10}{1140} \;=\;\frac{1}{114}$

June 7th, 2012, 01:32 PM   #3
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Re: permutation and combination

Quote:
 Originally Posted by talo0000 5 bottle of spoiled milk mixed with 15 bottle of good milk 1-if 3 bottle were selected at random, whit is the probability that they contain unspoiled milk 2-probability that the three selected at random are spoiled milk
thank you

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