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Brynlee
07-21-2013, 12:25 PM
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, 12:46 PM
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!!:):)

Brynlee
07-21-2013, 12:47 PM
Thank you Thomas!!:)