math

A student takes a true-false test that has 8 questions and guesses randomly at each answer. Let X be the number of questions answered correctly. Find P(6 or more)

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  1. Find P(6 or more) implies
    P(6) + P(7) + P(8)
    = C(8,6)(1/2)^6 (1/2)^2 + C(8,7) (1/2)^8 + C(8,8) (1/2)^8
    = (1/2)^8 (28+8+1) = 37/256

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