Imagine an urn with two balls, each of which may be either white or black. One of these balls is drawn and is put back before a new one is drawn. Suppose that in the first two draws white balls have been drawn. What is the probability of drawing a white ball on the third draw?

*Essai philosophique sur les probabilités*, Pierre-Simon Laplace, 1814

Click here to reveal the answer

The answer is: \(\dfrac{9}{10}\)