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John is eating jellybeans.In his bag of jellybeans he has 2 red, 2 green and 1 black jellybean left.Find the probability that the next 2 jellybeans he eats are both red?

Guest May 12, 2017
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#1
+399
+1

1 out of 5 + 1 out of 4

9 out of 20

or 0.45%

im not sure tho

Neptune  May 12, 2017
#2
+18629
+1

John is eating jellybeans.In his bag of jellybeans he has 2 red, 2 green and 1 black jellybean left.

Find the probability that the next 2 jellybeans he eats are both red?

Method 1:

probability  2 red $$= \frac{2}{5} \cdot \frac{1}{4} = \frac{2}{20} = \frac{1}{10} = 0.1\quad (10 \% )$$

Method 2:

probability  2 red

$$\begin{array}{|rcll|} \hline &= & \frac{\binom{2}{2}_{red}\binom{2}{0}_{green}\binom{1}{0}_{black}}{\binom52} \\ &=& \frac{1\cdot 1 \cdot 1 } { \frac52\cdot \frac41} \\ &=& \frac{2}{20} \\ &=& \frac{1}{10} \\ &=& 0.1\quad (10 \% ) \\ \hline \end{array}$$

heureka  May 12, 2017

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