Unit 1: 1 First, calculate the product by integer multiplication. 2. Look at a factor * * *, how many decimal places there are, just count the digits from the right side of the product and point to the decimal point. 3. If the number of decimal places multiplied by the product is not enough, add 0 in front, and then point the decimal point.

Unit 2: The decimal point of quotient should be aligned with the decimal point of dividend. Add 0 to the end of the decimal, and the size of the decimal remains the same. Write 0 as a placeholder unless it is not a quotient 0. Using the property of quotient invariance, fractional division can be transformed into integer division. Decimal digits are finite decimals, which are called finite decimals; The decimal places are infinite decimals, which are called infinite decimals. The decimal part of the cyclic decimal, that is, the numbers that appear repeatedly in turn, is called the cyclic segment of this cyclic decimal.

Unit 3: When you look at an object from one direction, you can see at most three sides of the object.