Can anyone explain to me how this problem is solved
Determine the probability that the first head appears on an odd number of flips i.e. X contains {1,3,5..}.
P[X] = summation starting at x = 1 to infinity (1/2)^(2x-1) = 1/2 / (1 - 1/4) = 2/3
Basically my question is, how is the...