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# Probability

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A drawer contains 3 white balls and 6 black balls. Two balls are drawn out of the box at random. What is the probability that they both are black?

Jun 4, 2021

#1
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A drawer contains 3 white balls and 6 black balls. Two balls are drawn out of the box at random. What is the probability that they both are black?

First ball drawn, there's a 6/9 probability that it will be black.   (6 black balls, 9 total balls)

If the first ball was black, it leaves 5 black balls in the drawer.

Now the probability that a black one is drawn is 5/8.                (5 black balls, 8 total balls)

The probability of both things happening, multiply the two probabilities together.

6/9 x 5/8 = 30/72       This reduces to 5/12   or in decimal form   41.67%

Jun 4, 2021

#1
+1

A drawer contains 3 white balls and 6 black balls. Two balls are drawn out of the box at random. What is the probability that they both are black?

First ball drawn, there's a 6/9 probability that it will be black.   (6 black balls, 9 total balls)

If the first ball was black, it leaves 5 black balls in the drawer.

Now the probability that a black one is drawn is 5/8.                (5 black balls, 8 total balls)

The probability of both things happening, multiply the two probabilities together.

6/9 x 5/8 = 30/72       This reduces to 5/12   or in decimal form   41.67%

Guest Jun 4, 2021