If the positions of the single digit and the ten digit of a two digit number are exchanged, the new two digit number will be 9 larger than the original two digit number. How many two digit numbers are there? What are their characteristics?

If the positions of the single digit and the ten digit of a two digit number are exchanged, the new two digit number will be 9 larger than the original two digit number. How many two digit numbers are there? What are their characteristics?

Let the original two digits be 10A + B, according to the meaning of the question: 10A + B + 9 = 10B + 1, the solution is: B = a + 1, because it can take 1 to 8 numbers, so the two digits have 8, they are respectively, 12, 23, 34, 45, 56, 67, 78, 89, they are two digits whose one digit is bigger than ten digits