It is wrong to say that the product of a decimal multiplied by an integer must be a decimal.

For example, 1.5*2=3, the product is an integer; 1.2*3=3.6, the product is a decimal; therefore, it is wrong that the product of a decimal multiplied by an integer must be a decimal. The product of a decimal times an integer may be an integer or a decimal. Decimals are a special form of expression of real numbers. All fractions can be expressed as decimals. The dot in a decimal is called the decimal point, which is the dividing number between the integer part and the decimal part of a decimal.

A decimal whose integer part is zero is called a pure decimal, and a decimal whose integer part is not zero is called a mixed decimal. Add or remove any number of zeros at the end of the decimal part, and the size of the decimal remains unchanged. By moving the decimal point n places to the right (or left), the decimal value will be expanded (or reduced) by n times the base.

Integer (integer) is a set of positive integers, zero, and negative integers. All integers constitute the set of integers, and the set of integers is a number ring. In the integer system, zero and positive integers are collectively called natural numbers. -1, -2, -3, ..., -n, ... (n is a non-zero natural number) are negative integers. Then positive integers, zero and negative integers form the integer system.

Integers do not include decimals or fractions. Unless otherwise stated, the numbers involved are integers, and the letters used also represent integers. Integers can be thought of as fractions with a denominator of 1. It has been a counting tool for humans since ancient times. It can be said that the process of abstracting from "1 cow, 2 cows" or "5 people, 6 people" into positive integers is quite natural.

Divisibility characteristics:

1. If the last digit of a number is an odd or even number, then the number can be divided by 2.

2. If the sum of all the digits of a number is divisible by 3, then the integer is divisible by 3.

3. If the last two digits of a number are divisible by 4, then the number is divisible by 4.

4. If the last digit of a number is 0 or 5, then the number is divisible by 5.

5. If a number is divisible by 2 and 3, then the number is divisible by 6.