Question 271350
If you have a bag of marbles; 7 red, 5 green, and 8 blue, what's the probability of getting at least 2 red marbles in 3 draws from the bag, with replacement? 
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Binomial Problem:
n = 3 ; p = 7/20
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P(2<= x <=3) = 3C2(7/20)^2(13/20) + 3C3(7/20)^3(13/20)^0
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= 0.2389 + 0.0429
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= 0.2818
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Cheers,
Stan H.