As the end of the term approaches, children always make mistakes when doing calculation problems. Many parents have responded that they don’t know why their children always ignore some mathematical rules, which is very troublesome. Today, the editor specially compiled 15 rules of primary school mathematics for parents’ reference.
1 When calculating two-digit addition, remember three rules:
1: Align the same digits;
2: Add from the ones digit;
3: When the ones digit reaches 10, advance 1 to the tens digit.
2 When subtracting two-digit numbers, remember three rules:
1: Align the same digits;
2: Subtract from the ones digit;
3: If the units digit is not enough to subtract, go back 1 from the tens digit, add 10 to the ones digit and then subtract.
3 Mixed operation calculation rules
1. In calculations without brackets, if there are only additions, subtractions or only multiplications and divisions, operations must be performed in order from left to right;
2. In calculations without brackets, there are multiplications, divisions, additions and subtractions. Yes, you must first calculate multiplication and division and then addition and subtraction;
3, if there are parentheses in the calculation, you must calculate what is inside the parentheses first.
4 The four-digit reading method
1, read in order from the high digit, the thousands digit reads thousands, the hundreds digit reads hundreds, and so on;
2, if there is a 0 or two 0s in the middle, only read one "Zero";
3, no matter how many zeros there are at the end, it will not be read.
5 Four-digit writing method
1, starting from the high position, write in order;
2. For thousands, write the number in the thousands place, for hundreds, write the number in the hundreds place, and so on, there is no one in the middle or at the end. , just write "0" on which bit.
6 When subtracting four digits, pay attention to the three lines
1. Align the same digits;
2. Subtract from the ones digit;
3. If any digit is not subtracted enough, return 1 from the previous digit, add 10 to the base digit, and then subtract.
7 Multiplication of a single digit Multiple digits Multiplication rules
1. Starting from the ones digit, multiply each digit of the multi-digit number by a single digit in turn;
2. Whichever digit has the best multiplication number reaches tens, move forward. Several.
8 The divisor is a one-digit division rule
1. Starting from the high-digit division of the dividend , each time the divisor is used to divide the previous digit of the dividend, if it is smaller than the divisor, then try to divide the first two digits;
2. Division by the divisor Whichever digit you reach, write the quotient on that digit;
3. Every time you find a quotient, the remaining number must be smaller than the divisor.
9 A factor is the multiplication rule for two-digit numbers
1. First use the number in the two-digit ones digit to multiply another factor, and the last digit of the number will be aligned with the two-digit ones digit;
2. Then use the two-digit number Multiply the number in the tens digit by another factor, and align the last digit of the number with the two tens digits;
3, and then add the two multiplied numbers.
10 The divisor rule is that the divisor is a two-digit number
1. Starting from the high digit of the dividend, try dividing the first two digits of the dividend with the divisor. If it is smaller than the divisor,
2. Write the quotient on the digit of the dividend you divide to;
3. Every time a quotient is found, the remaining number must be smaller than the divisor.
110,000 The reading rules for are
1. Read the ten thousand level first, and then read the next level;
2. The number of ten thousand should be read according to the one level reading method, and then add the word "ten thousand" at the end;
3 , No matter how many zeros there are in the last digit of each level, it will not be read. If there is one 0 or several consecutive zeros in other digits, only one "zero" will be read.
12 multi-digit reading rules
1. Starting from the high position, read one level at a time;
2. When reading hundreds of millions or ten thousand levels, read according to the reading method of series, and then add "billions" at the end. " or "ten thousand" characters;
3, the 0 at the end of each level is not read, and other digits with a 0 or several consecutive 0s are only read as a zero.
13 Comparison of decimal sizes
To compare the sizes of two decimals, look at their integer parts first. The number with the larger integer part is larger. If the integer part is the same, the number with the larger tenth place is larger, and the tenths are also the same. , the number with the larger percentile is larger, and so on.
14 Decimal addition and subtraction calculation rules
To calculate decimal addition and subtraction, first align the decimal points (that is, align the numbers on the same digits), then calculate according to the integer addition and subtraction rules, and finally align the horizontal lines in the resulting numbers. At the decimal point position, click the decimal point.
15 Calculation rules for decimal multiplication
To calculate decimal multiplication, first calculate the product according to the rules of multiplication, and then look at the total number of decimals in the factor, count the number from the right side of the product, and click on the decimal point.
