Two similar permutation and combination questions, in 1.2.3.4 these four numbers constitute three digits without repeating numbers, in which the odd number has 2. Take any three digits from the six numbers 0-5 to make up the unrepeated number, of which the even number is Please let me know by permutation,

Two similar permutation and combination questions, in 1.2.3.4 these four numbers constitute three digits without repeating numbers, in which the odd number has 2. Take any three digits from the six numbers 0-5 to make up the unrepeated number, of which the even number is Please let me know by permutation,

1. In the four numbers of 1.2.3.4, form the three digits without repetition, in which the odd number has
A bit can only be one of 1 and 3. There are two methods
There are a (3,2) methods
There are 2 * a (3,2) = 12 odd numbers
2. Take any three digits from the six numbers 0-5 to make up the unrepeated number, of which the even number is
Classification:
(1) The end is zero, other bits are unlimited, there are 20 methods of a (5,2) = 5 * 4 = 20
(2) If the end is not 0, there are two methods. There are four methods for 100 bits and four methods for individual bits. There are 32 methods for 2 * 4 * 4
There are 20 + 32 = 52 even numbers

A 6-digit number composed of 123456 and without repeated digits. If the odd number is not adjacent and 4 is not in the fourth digit, how many such numbers are there, Lu

Odd numbers are not adjacent. There are four ways to arrange them
Odd even even odd,
Parity parity
Parity parity
Even odd even odd,
Discuss each one separately
1, parity
First row 4,2; second row 2,6,2; last row 1,2,3,3! = 6
Total 2 * 2 * 6 = 24 species
The rest is the same
2, parity, 6 * 6 = 36
3, parity, parity, 6 * 6 = 36
4, even odd, 2 * 2 * 6 = 24
There are 120 kinds in total

How many odd and even four digit numbers are there in 0, 2, 5, 6, 7 and 8?
I don't know much about it at the beginning. Please calculate twice instead of subtracting 300 the second time. It's better to just calculate. I don't like to use permutation to calculate the total

Odd number: because you want odd number, so the last digit is 5 or 7, there are 2 numbers to choose, the first digit can not be 0, so the first digit has 4 numbers to choose, it is 3 even numbers, it is 2, 6, 8, and 1 odd number, because the last odd number is chosen, the second digit also has 4 numbers to choose (the second digit can choose 0), the third digit has 3 numbers