If a coin is tossed n times, then find the probability that the head appears odd number of times.

Explanation

Total number of cases = `2^(n)`
If head appears odd number of times (1, 3, 5, … times), then Number of favourable ways = `(.^(n)C_(1) + .^(n)C_(3) + .^(n) C_(5) +...) = 2^(n-1)`
`therefore` Required probability = `(2^(n-1))/(2^(n)) = (1)/(2)`