The chance Consider a fair coin tossed 100 times. a) what is the probability of landing heads 55 times or more? b) what is the chance of getting between 40 and 60 tails on the 100 flips?

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a) The probability of landing head = 1/2

Since each roll is independednt, then prbability of landing heads 55 time or more = probability of landing heads 55 times + probability of landing 56 times + ...+ probability of langing heads 100 times

= (1/2)^55 + (1/2)^56 + ...+ (1/2)^100

= (1/2)^55 [ 1 + 1/2 + (1/2)^2 + ... + (1/2)^ 45]

B) Probability for getting between 40 and 6o tails = probability of getting 41 tails + P(42 tails) + ...+ P(59 tails)

= (1/2)^41 + (1/2)^42 + .... (1/2)^59)

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