The smallest two digits are 10. The number of digits of a natural number is called the number of digits. A number containing one digit is one digit, a number containing two digits is two digits, a number containing three digits is three digits, and a number containing n digits is n digits.

The most popular two-digit number is 99, and their difference is 89. Because less than 10 is 9, 9 is a single digit, and 10 is the smallest two digits. 100 is greater than 99, and 100 is a three-digit number, so 99 is the largest two-digit number. There are no two digits greater than 99 and no two digits less than 10.

In the formula, from the right, the first one is one digit, and the second one is ten digits. 20 yuan has two 10 yuan, or 20 yuan has 20 1 yuan. The minimum digit is 1, the minimum digit is 10, and the maximum digit is 9. The starting point on the ruler is indicated by 0.