# How many three-digit numbers can be made from the numbers 1, 2,3,4,5 if: a) the numbers are not repeated?

How many three-digit numbers can be made from the numbers 1, 2,3,4,5 if: a) the numbers are not repeated? b) can the numbers be repeated? There are 5 different ways to select the first digit (left in a three-digit number). After the first place is taken, for example, by the number 2, there are four digits left to fill the second place. A choice of three numbers remains to fill the third place. Therefore, according to the multiplication rule, there is 5. 4 . 3 = 60 ways of arranging numbers, that is, the required number of three-digit numbers is 60. (Here are some of these numbers: 243, 541, 514, 132, …) It is clear that if the numbers can be repeated, then there are 5 three-digit numbers. five . 5 = 125. (Some of them are: 255, 333, 414, 111, …) Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.