Imagine that you have a coin that is biased – that is, in a long series of tosses it won’t come up with 50% heads and 50% tails. Alas, you don’t know the extent of the bias. How can you use the coin to generate a random series of zeros and ones?
The sequence Heads-Tails is as likely as Tails-Heads, no matter the extent of the bias. And so you toss the coin twice for each trial. You ignore the Heads Heads and Tails Tails sequences, and assign a 1 to Heads Tails, and a 0 to Tails Heads. That way, you will generate a random sequence of 1s and 0s from a biased coin. Did you solve it? Any other answers?
I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here). You can try 101 of the puzzles for free here.