Here our major task is to make the biased coin fair: This can be done in the following way: Let the probability of tossing a coin and getting a head be p. And therefore the probability of getting a tail be (1 - p) Then perform the following steps: This will be a fair coin toss because now the probability of considering a head is equivalent to probability of coming up of a tail followed by probability of coming up of a head = (1 - p ) * p And probability of considering a tail is equivalent to probability of coming up of a head followed by probability of coming up of a tail = p* (1 - p ) Therefore the probability of considering a tail is thus equivalent to the probability of considering a head. Therefore this is a fair toss now. Hence, proved.