<PRE><B>Question 175661</B>
6 blue
8 red
5 purple
9 green
2 clear
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30 total
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probability of getting a clear marble on the first pick is 2/30 because there are 2 clear marbles out of a total of 30 marbles in the box.
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probability of getting a purple marble on the second pick regardless of what was chosen on the first pick is 5/30 because there are 5 purple marbles out of a total of 30 marbles in the box once again since you put the marble you took on the first pick back in the box.
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the probability of getting a clear marble on the first pick, putting it in the box, and then getting a purple marble on the second pick is 2/30 * 5/30.
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if the probability of an event happening is x, and the probability of another event happening is y, then the probability of both events happening is x*y.
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by replacing the clear marble in the box, you made the two individual events independent of each other.  if you did NOT replace the clear marble, then the probability of getting a purple marble on the second pick would have changed.
in that case it would have been 5/29 rather than 5/30.
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