You can put this solution on YOUR website! IF YOU FLIP A COIN 7 TIMES WHAT IS THE PROBABILITY THAT IT WILL LAND ON HEADS 3 TIMES?
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Binomial Problem with n = 7 and p = 1/2.
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P(x=3) = 7C3(1/2)^3*(1/2)^4 = 35/128
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Cheers,
Stan H.