Question

A fair coin is tossed 100 times. The probability of getting

tails an odd number of times is

• A. ½
• B. 1/8
• C. 3/8
• D. None of these

Answer 1

Answer: (A)

½

Answer 2

Let X denote the number of tails. Then, X is a binomial variate with parameters n=100 and p=1/2.

Therefore,

Required probability

$= \mathrm { P } ( \mathrm { X } = 1 ) + \mathrm { P } ( \mathrm { X } = 3 ) + \ldots \ldots + \mathrm { P } ( \mathrm { X } = 99 )$