This bag had 35 green, some black and 3 red marbles. Reaching blindfolded, the probability of picking a red is 1/23. How many black marbles are there.

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  1. let B = the number of black marbles.

    probability of drawing red:
    3/(35 + 3 + B) = 1/23

    3/(38 +B) = 1/23
    69 = 38 + B

    B = 31

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    posted by drwls

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