You can put this solution on YOUR website! IF WE ROLL A DICE 15 TIMES, WHAT IS THE PROBABILITY THAT WE WILL ROLL A 6 AT LEAST 13 TIMES?
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Binomial Problem with n = 15 and p = 1/6
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P(13<= x <=15) = 1 - P(0<= x <=12) = 0.00000000574455..
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Cheers,
Stan H.