3. How many different three digits can 5, 0 and 9 make up? Is there a formula for a problem like this?

3. How many different three digits can 5, 0 and 9 make up? Is there a formula for a problem like this?

This is a scheduling problem. There is a formula that can be solved directly. Because the first number is not 0, there are only three possibilities for any one of 3, 5 and 9. The last two digits can be 0. The ten digits can be selected from the remaining three digits. One digit can only be selected from the remaining two digits, and there are three possibilities
So there's a total of 3x3x2 = 18

In the four numbers of 0, 1, 2 and 5, choose three different numbers to form a number that is also a multiple of 2, 3 and 5. The maximum three digits are______ The minimum three digits are______ ．

In the four numbers of 0, 1, 2 and 5, choose three different numbers to form a multiple of 2, 3 and 5. The maximum three digits are 510; the minimum three digits are 150; so the answer is 510150

1.2.3.4.5.6.7.9 form two four digit numbers and minimize the difference. What is the difference?

5123 and 4976, 147
In order to minimize the difference between the two numbers, the larger number should be as small as possible, and the smaller number should be as large as possible. The closer the two numbers are, the better. First, divide the above eight numbers into two groups, namely 1.2.3.4 and 5.6.7.9. According to the above principle, select the thousand digits as 4 and 5, and then select the hundred digits, ten digits and you