The section “Getting Fairness from Biased Sources” explains how you can use a biased coin to get fair coin flips by flipping the coin twice. However, sometimes doing two flips produces no result, so...

The section “Getting Fairness from Biased Sources” explains how you can use a biased coin to get fair coin flips by flipping the coin twice. However, sometimes doing two flips produces no result, so you need to repeat the process. Suppose that the coin produces heads three-fourths of the time and tails one-fourth of the time. In that case, what is the probability that you’ll get no result after two flips and have to try again?