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Probability

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by Lisak » Thu May 10, 2012 2:30 pm
There are 38 balls in a basket. The balls are selected one at a time and add back into the basket. During the first 4 drawings 4 different balls are selected. What is the probability that on the 5th drawing one of those same balls will be selected?
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Source: — Problem Solving |

by mathbyvemuri » Thu May 10, 2012 10:42 pm
This is a draw with replacement case.
We need one of the four different balls in the 5th draw.
Required possibilities = 4 (As one out of a particular four is required)
All possibilities = 38 (As any one out of 38 may come in the draw)
Probability = [spoiler]4/38 = 2/19[/spoiler]
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