Ordinary primary school students begin to learn elementary arithmetic in the third grade, and learn addition and subtraction mixed operations in the second grade. The fourth grade involves the elementary arithmetic of decimals, and the elementary arithmetic of decimals and fractions in the fifth grade is basically the integration of the whole primary school knowledge. However, each textbook and each version will have different arrangements for knowledge learning time.
Extended data:
Fractional algorithm:
1, addition and subtraction of fractions: add and subtract fractions with denominator, only add and subtract numerators, and the denominator remains unchanged. Fractions of different denominators are added and subtracted, first divided, then added and subtracted.
2. The law of fractional multiplication by integer: take the product of fractional numerator multiplied by integer as numerator, and the denominator remains unchanged.
3. Fractional rule: use the product of molecular multiplication as the numerator and the product of denominator multiplication as the denominator.
4. Dividing the score by an integer (except 0) is equal to multiplying the score by the reciprocal of this integer.
5. A number divided by a fraction is equal to the number multiplied by the reciprocal of the fraction.
6. At the end of the score calculation, the score must be converted into the simplest score.
7. The basic nature of the fraction: the numerator and denominator of the fraction are multiplied or divided by the same number at the same time (except 0), and the size of the fraction remains unchanged.