The central problem for players is to find and bet with a positive expected win. But players also need to know how to manage their money, t. e. How much . In the stock markets (including the securities market), the problem is similar to this one, but more complex. A player who is now an investor is looking for . In both of these cases, we explore the use of the Kelly criterion, which maximizes the expected value of the logarithm of income. This criterion is known to economists and financial theorists under such names as , maximization of logarithmic utility, strategy of optimal growth, criterion of capital growth, etc. d. The author began the practical application of the Kelly criterion by using it to account for cards in blackjack. We will present some useful formulas and techniques to answer various natural questions about this that arise in blackjack and other gambling. We will then illustrate its recent use in successful betting systems for sports sweepstakes. In conclusion, we will discuss its application to the securities market, where these methods helped the author to make for thirty years a total of 80 billion dollars.