Unit 1 Decimal Multiplication
1, decimal times integer:
Meaning: A simple operation to find the sum of several identical addends.
For example, 1.5×3 represents a simple operation to find the sum of three 1.5 (or what is three times 1.5).
Calculation method: first expand the decimal into an integer; Calculate the product according to the law of integer multiplication; Look at a factor * * *, how many decimal places there are, and count the decimal points from the right side of the product.
2. Decimal times decimal:
Meaning: Find a fraction of this number.
For example, 1.5×0.8 is how much is eight tenths of 1.5 (or how much is 1.8 multiplied by 1.5).
Calculation method: first expand the decimal into an integer; Calculate the product according to the law of integer multiplication; Look at a factor * * *, how many decimal places there are, and count the decimal points from the right side of the product.
Note: After calculating the product with integers, you should remove the 0 at the end of the decimal, that is, simplify the decimal; When the number of digits is not enough, use 0 to occupy the place.
3. Rule: a number (except 0) is multiplied by a number greater than 1, and the product is greater than the original number; A number (except 0) is multiplied by a number less than 1, and the product is less than the original number.
4. There are generally three methods to find the divisor: rounding method; Become law; Tailing method
5. Calculate the amount of money and keep two decimal places, indicating that the calculation has reached the point; Keep one decimal place, indicating that the angle has been calculated.
6. The order and law of decimal four operations are the same as those of integers.
Unit 2 Knowledge Points
1, number pair: consists of two numbers, separated by commas and enclosed by brackets. The numbers in brackets are the number of columns and the number of rows from left to right, that is, "columns first, then rows".
2. Function: A set of numbers set the position of a unique point. Longitude and latitude are the principles.
Example: In the grid diagram (plane rectangular coordinate system), it is represented by several pairs (3, 5) (third column, fifth row).
Note: In the plane rectangular coordinate system, the coordinates on the X axis represent columns and the coordinates on the Y axis represent rows. For example, the number pair (3, 2) represents the third column and the second row. Logarithm (x, 5) remains unchanged, indicating the horizontal line, and the number of columns (5, y) remains unchanged, indicating the vertical line. (A number is uncertain and a point cannot be determined)
3. The number of lines translated left and right remains unchanged; The number of columns in the chart that move up and down remains the same.