You meet a nasty dog in a dark alley. The dog has a bag and the bag has a pebble in it. The pebble is either black or white. The dog then adds a white pebble and shakes up the bag. He then asks you to take a pebble from the bag without looking inside it. What are your chances of taking out a white pebble?
As ever, please do NOT post your answers, but do say if you think you have solved it and how long it took. Solution on Monday.
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.