Use 1,2,3,4,5,6,7, seven numbers to make up seven digits without repetition, in which the odd number is more than the even number? How many even numbers are not adjacent? How many even numbers are on the even digits?

One
4 * 6! - 3 * 6! = 720, select a bit first
Two
There are 10 kinds of non adjacent 3 bits from 7 bits
135,136,137,146,147,157,246,247,257,357
10*3!*4!=1440
Three
3!*4!=144

Arrange 1,2,3,4,5,6,7 into seven digits without repetition. There is an odd number between 1 and 2. How many numbers are there without even number?

A2 / 2 * C1 / 3 * A5 / 5 = 2 * 3 * 5 * 4 * 3 * 2 * 1 = 720 species

How many seven digit numbers without repetition can be made up of three even and four odd numbers out of nine numbers from 1 to 9 What is a seven digit number without repeating numbers? What is a non repeating number? Is it 1234554321? Is it called repeated number? Or as long as there is 12345, there can not be these five numbers in the back. What's the fallacy

First of all, if there are no duplicate numbers, each number is unique in this number, for example, 12345, then the numbers 1, 2, 3, 4, 5 cannot appear in the following numbers
In the number of 1 ~ 9, there are 5 odd numbers and 4 even numbers
According to the requirements of the question design, there are: C (4) 3 * C (5) 4 * P (7) 7
Here we use the full permutation P (7) 7 at the end. The reason is that after selecting the required number from the specified odd and even numbers, then the change of position is the permutation problem, that is, the selected 7 numbers should be arranged. I don't know if you understand it

Using 1,2.3,4,5 to form a five digit number without repeating numbers, in which there are exactly two even numbers sandwiched between the odd numbers 1 and 5. How many such five digits are there I can't understand the title itself, let alone why we have to do this; or list the five digits that meet the requirements

12453 14253 31245 31425 52413 54213 35241 35421
I wonder if we can see the law

Using 1,2.3,4,5 to form a five digit number without repeating numbers, in which there are exactly two even numbers sandwiched between the odd numbers 1 and 5. How many such five digits are there

There were 6 lxx5 cells;
6 pieces of 5xxx1;
2 31xx5;
2 35xx1;
1 x 53 2;
5xx13 2
Total 6 + 6 + 2 + 2 + 2 + 2 = 20

How many 3-digit, 3-digit, even and 3-digit odd numbers can be made up of six numbers: 0, 1, 2, 3, 4, 5

As long as the first three digits is not zero, that is, 5 * 5 * 4 = 100 kinds
Three is even, as long as there are three digits at the end of 0,2,4, 100-3 * 4 * 4 = 52 kinds (because 0 cannot be the first place, it will be more troublesome to calculate directly. The calculation here is to calculate the number of three odd numbers first, and then subtract the number of odd numbers from the total three digits)
Three odd 3 * 4 * 4 = 48 species

The five digit number of zero, one, two, three and four is composed of five digits without repetition, in which there is exactly one even number sandwiched between two odd numbers, and the number of five digits is () A. 48 B. 36 C. 28 D. 12

There are three even numbers and two odd numbers in 0, 1, 2, 3 and 4, which can be discussed in three cases: 1. 0 is sandwiched in the middle by odd numbers. First, consider the order of odd numbers 1 and 3, and there are two cases; then take 1, 0 and 3 as a whole and arrange them with 2 and 4. There are 6 cases of A33 = 6

1.5, 2 / 3, and 0.4 can be proportional to another number, which can be (), (), or ()

1.5/(2/3)=0.4/(8/45)
1.5/(2/3)=0.9/0.4
1.5/0.4=2.5/(2/3)
These three numbers are 8 / 450.92.5

5,2 | 3 and 0.4 can form a proportion with another number, which can be (), (), ()

5, 2|3 and 0.4 can form a proportion with another number, which can be (3), (25 / 3), (4 / 75)

When a = (), (), or (), these four numbers can form a proportion Yellow ball 10 brother, basketball 11, each time touch a ball, at least () times

1；9；0.04

Use 1,2,3,4,5,6,7, seven numbers to make up seven digits without repetition, in which the odd number is more than the even number? How many even numbers are not adjacent? How many even numbers are on the even digits?