Комбінаторика

Hello to all viewers of my channel! In this video we will talk about combinatorics. 00:00 - What is combinatorics 00:19 - The sum rule. There are 3 apples and 4 pears on a plate. In how many ways can you take one fruit from the plate? 01:04 - There are 3 apples and 4 pears on a plate. In how many ways can you take two fruits from the plate - one pear and one apple? 02:29 - There are 3 apples and 4 pears on a plate. In how many ways can you take two fruits from the plate? 03:30 - A cafe offers a menu of 3 first courses, 6 second courses and 5 third courses. How many ways are there to choose a three-course lunch (one dish of each type)? 04:13 - A student must choose a topic for an essay from a list of 15 topics in algebra and 12 topics in geometry. In how many ways can he make a choice? 05:06 - How many three-digit numbers are there that are all odd? 06:39 - How many three-digit numbers are there that are all even? 07:56 - How many three-digit numbers are there that are all even and cannot be repeated?