How many of the 3 digits without repetition are composed of 1.2.3.4.5.6

The characteristic of the multiple of 9 is that the sum of all digits is equal to 9123456, and the combination of integers that can be 9 has 126, 135, 144, 234, 333, among which 126, 135, 2334 can form 6 different three digits respectively, so there are 18 144s in total, which can only form 3 different digits, and 333 can only form one

Use 1, 2, 3, 4, 5 and 6 to form a four digit number without repetition, which is a multiple of 6. There are ()
A. 24 b.42 c.48 d.60

It is a multiple of 6. The number of digits is even and the sum of four digits can be divided by 3
When the one digit is 2, the other three digits can be 1,3,6 (there are six kinds of four digits) or 1,4,5 (there are six kinds of four digits) or 3,4,6 (there are six kinds of four digits)
When the one digit is 4, the other three digits can be 1,2,5 (six kinds of four digits) or 3,5,6 (six kinds of four digits) 2,3,6 (six kinds of four digits)
When one bit is 6, the other three bits can be 1,2,3 (6 kinds) or 2,3,4 (6 kinds) or 3,4,5 (6 kinds) or 1,3,5 (6 kinds)
So there are 60 four digit numbers

How many unrepeated four digit numbers are composed of the five numbers 1.2.3.4.5? How many of them are multiples of five?
Just say the second answer.

1. The first digit can take any one of the five, the second digit can take one of the remaining four, and so on, there are a total of 5 * 4 * 3 * 2 = 120 species
2. There is only one way to take the individual position, that is, there are four other ways to take the 5 and 10 positions, and so on, there are 24 kinds of 1 * 4 * 3 * 2

How many of the 3 digits without repetition are composed of 1.2.3.4.5.6