After exchanging the position of a two digit number with a number above ten, a new two digit number is obtained, which is equal to the original two digit number After a two digit digit digit and a digit above ten are exchanged, a new two digit digit is obtained, which is equal to 2 / 9 of the original two digits, and the original two digits are obtained

After exchanging the position of a two digit number with a number above ten, a new two digit number is obtained, which is equal to the original two digit number After a two digit digit digit and a digit above ten are exchanged, a new two digit digit is obtained, which is equal to 2 / 9 of the original two digits, and the original two digits are obtained

First of all, if it is a two digit number, then the new two digit number is 4.5 times of the old one, and it is still a two digit number, then the new number certainly has no decimal
Let the old number be 10x + y, then the new number be 10Y + X, and 0 ≤ x ≤ 9,0 ≤ y ≤ 9
Then 10Y + x = 4.5 (10x + y) = > 5.5y = 44x = > 0.5y = 4x = > y = 8x
So, x = 1, y = 8, so the number is 18

For a three digit number, the ten digit number is 1 larger than the one digit number, the hundred digit number is 2 larger than the ten digit number, and there is another two digit number
For a three digit number, the ten digit number is 1 larger than the one digit number, and the hundred digit number is 2 larger than the ten digit number. For another two digit number, the ten digit number is the same as the three digit number, which can be expressed by a, and the one digit number is 3 smaller than the ten digit number. Please use the algebraic formula containing a to express the product of the two numbers, and simplify the algebraic formula. If a = 4, express the two numbers
The number of ten digits is the same as that of three digits
I always think this sentence is wrong, but that's what the paper says.

If the first three digit number is a, then the ten digit number is a + 1; if the hundred digit number is a + 3, then the three digit number is 100 (a + 3) + 10 (a + 1) + a = 111a + 310; if the two digit number is a, then the two digit number is 10A + (A-3) = 11a-3; if the two digit number is multiplied by (111a + 310) * (11a-3) = 12

The mathematics of each digit of a number is different, and the sum of the number on the individual digit and the number on the ten digit is equal to the number on the hundred digit, and the sum of the number on the ten digit and the number on the hundred digit is% 2
The mathematics of each digit of a number is different, and the sum of the number of the individual digit and the number of the ten digit is equal to the number of the hundred digit, the sum of the number of the ten digit and the number of the hundred digit is equal to the number of the thousand digit, and the sum of the number of the hundred digit and the number of the thousand digit is equal to the number of the ten thousand digit?

Finally!
Let a * 10000 + b * 1000 + C * 100 + D * 10 + e = f (F is the number)
E + D = C, D + C = B, C + B = a are obtained
Since this number is a five digit ten thousand digit number, set the maximum ten thousand digit number as 9
We got 95413
In the same way, the minimum is 74312

For a two digit number, its ten digit number plus seven times of the one digit number is still equal to the two digit number. Such a two digit number has ()
A. One B. two C. three D. four

Let ten digits be x and one digit be y. according to the meaning of the question, we get that x + 7Y = 10x + y, that is, 3x = 2Y, while 1 ≤ x ≤ 9, 0 ≤ y ≤ 9, and X and y are all integers. According to the conditions, the values of X and y can be divided into three groups: 2, 3; 4, 6; 6 and 9, that is, there are three such two digits: 23, 46 and 69