Brynlee

07-21-2013, 11:25 AM

SAT math Probability question

In a box of 9 marbles, 3 are white. Find the probability of three marbles chosen from the box are all white?

Thanks!!:)

Thomas

07-21-2013, 11:46 AM

SAT math probability question

In a box of 9 marbles, 3 are white. Find the probability of three marbles chosen from the box are all white?

The probability of choosing a white marble in the first selection is \frac{3}{9}=\frac{1}{3},

the probability of choosing a white marble in the second selection is \frac{2}{8}=\frac{1}{4},

and finally, the probability of choosing a white marble in the third selection is \frac{1}{7}.

Multiplication Principle: When there are two or more choices to make, the

total number of possible ways that they can both occur is found by multiplying the

numbers of options for each choice.

Therefore, P(all \ three \ marbles\ are \ white)=\frac{1}{3} \cdot \frac{1}{4} \cdot \frac{1}{7}=\frac{1}{84}

Hope these help!!:):)

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