Maurice Borisovich Kraitchik (April 21, 1882 – August 19, 1957) was a Belgian mathematician and populariser.
His main interests were the theory of numbers and recreational mathematics.He was born to a Jewish family in Minsk.
He wrote several books on number theory during 1922–1930 and after the war, and from 1931 to 1939 edited Sphinx, a periodical devoted to recreational mathematics.
Each is ignorant of the contents of the two wallets.
The game is as follows: whoever has the least money receives the contents of the wallet of the other (in the case where the amounts are equal, nothing happens).
One of the two men can reason: "Suppose that I have the amount A in my wallet.
That's the maximum that I could lose.
If I win (probability 0.5), the amount that I'll have in my possession at the end of the game will be more than 2A.
Therefore the game is favourable to me." The other man can reason in exactly the same way.
Norton, 1942 and London: George Allen & Unwin Ltd, 1943, 328 pages (revised edition New York: Dover, 1953)
Alignment Charts, New York: Van Nostrand, 1944