Keyword: «the greatest common divisor of two integers»

The author presents the methodological paper of the lesson of the mathematical society on the topic "The Euclidian algorithm", designed for students of 7th, 8th and 9th grades. The topic is designed for 2–3 hour lesson. We consider the origin of the word algorithm. The essence of the Euclidean algorithm is presented in the form of two formulas. The author also provides the examples of the application of the Euclidean algorithm.