In the second step, we learn 10 plus a single digit, such as10+3 =10+7 = 4+10 = we should learn step by step and give children appreciation and encouragement in time.
The third step is to learn how to add a number to two numbers within 20, such as 13+5 =11+8 =17+2 = to guide children to know that13 is 10 and 3. So is subtraction.
The fourth step is to learn the method of adding one digit to another (rounding off 10). For example, 8+5= this requires children to have a very good combination (especially 10). To make children feel that 8 is short of 10, divide 5 into 2 and 3, then add 8 and 2 to 10 and add 3.
Step 5, learn to subtract, 15-6=5 minus 6 is not enough, and subtract 6 from the previous 10,10-6 = 4,4+5 = 9.
Extended data 1, additional
A, Integer and Decimal: the same digit is aligned, starting from the low digit and full decimal into one.
B. Fractions with the same denominator: addition of molecules with the same denominator; Fractions with different denominators: divide first, then add.
Step 2 subtract
A. Integer and Decimal: the same digits are aligned, and the digits decrease from low order. If the digits are not enough, subtract ten and then subtract.
B, the same denominator score: the denominator is unchanged, and the numerator is subtracted; Denominator score: divide first, then subtract.
Step 3 increase
A. Integer and Decimal: Multiplied by the number on each bit of the multiplier, and which bit will the last bit of the number match. Finally, add the product, the factor is decimal, and the decimal places of the product are the same as those of the two-digit factor.
B. Fraction: The product of numerator multiplication is numerator, and the product of denominator multiplication is denominator. The first reducible result should be simplified.
Step 4 separate
A, Integer and Decimal: How many digits are there in the divisor? Look at the first few digits of the dividend first (if it is not enough, look at one digit), and write the quotient on which digit other than the dividend. The divisor is a decimal, which is converted into an integer before division. The decimal point in the quotient is aligned with the decimal point of the dividend.
A divided by B (except 0) equals the reciprocal of A divided by B. ..