Hello! ! ! 1. Calculation rules of decimal addition and subtraction: align the decimal points of each number and calculate according to the law of integer addition and subtraction. In the obtained number, align the decimal point on the horizontal line and point the decimal point. 2. Calculation rules of decimal multiplication and division: Calculate the product (or quotient) according to integer multiplication and division. For multiplication, it depends on how many digits the multiplier and the multiplicand have. Fill in zero when it is not enough. For division, the decimal point of quotient should be aligned with the decimal point of dividend. 3. Fraction addition and subtraction algorithm: use the denominator to add and subtract fractions, as long as the numerator is added and subtracted, the denominator remains unchanged; To add and subtract the scores of different denominators, we must first divide (find the least common multiple of denominator, and expand the same multiple of numerator denominator at the same time, so that different denominators become the same denominator, and then operate according to the same denominator score; Add and subtract fractions, add and subtract fractions and integer parts respectively, and then combine the results. 4. Multiplication algorithm of fractions: take the product of molecules as numerator and the product of denominator as denominator. When multiplying with a fraction, first turn the fraction into a false fraction, and then multiply. 5. Fraction division algorithm: transpose the numerator and denominator of the fraction as divisors into multiplication. Secondly, the scores were reduced.