There are four points in the classification exercise of simple mathematics operations in primary schools: a. In general, the calculation order of the four operations is: first calculate when there are brackets, then calculate when there are no brackets, and only when there are operations of the same level, from left to right. B, because some calculation problems have their own characteristics, then using the algorithm can make the calculation process simple and not easy to make mistakes. C, note that for the same calculation problem, the result calculated by simple method should be the same as that calculated without simple method. We can check whether our calculation is correct by comparing the results obtained by the two calculation methods. D. In the calculation of fractional multiplication and division, if there is a fraction, it must be converted into a false fraction and then calculated. First, when a calculation problem has only the same level of operations (only multiplication and division or only addition and subtraction) and there are no brackets, we can "move with signs". (a+b+c=a+c+b，a+b-c=a-c+b，a-b+c=a+c-b，a-b-c = a-c-b； A×b×c=a×c×b, a \b \c = a \c \b, a×b \c = a \c×b, a \b×c = a×c \b),12.06+5. It used to be negative, but now it is positive. a+b+c=a+ (b + c)，a+b-c=a +(b-c)，a-b+c = a-(b-c)，a-b-c = a-(b+c)； 933-15.7-4.341.06-19.72-20.28 7-3+8+2-11+7+3 b, when a calculation problem only has multiplication and division. It used to be division, but now it's multiplication. A×b×c=a×(b×c), a×b÷c=a×(b÷c), a÷b÷c=a÷(b×c), a÷b× c = a÷. But when the brackets after the minus sign are removed, the addition in the original brackets will now be reduced; It used to be negative, but now it is positive. There are no brackets now, so you can move with symbols. )A+(b+ C)= A+B+CA+(B-C)= A+B-CA-(B-C)= A-B+CA-(B+C)= A-B-C； 19.68-(2.68+2.97) 5.68+(5.39+4.32)19.68-(2.97+9.68) 7+(-) 5-(-) b, when an arithmetic problem only has multiplication, division and brackets. But when the brackets after the division sign are removed, the multiplication in the original brackets now becomes division; It used to be division, but now it's multiplication. There are no brackets now, so you can move with symbols. )A× (b× c) = A× b× c，A× (b÷c) = A× b÷c，A÷ (b× c) = A÷b÷c，A÷。 1.25× (8 ÷ 0.5) 0.25× (4×1.2)1.25× (213× 0.8) 9.3 ÷ (4 ÷) 0.92×1.41+0.92× -×1.3×1.6-1.3×/kloc. 3.2×12.5× 251.25× 88 3.6× 0.25c, cleverly divided into multiplication (division equals to multiply by 4, division equals to multiply by 8, ...) 7.6 ÷ 0.25 3.5 ÷ 0.10. Let our formula satisfy the conditions of multiplication and distribution law:1.8× 99+1.8× 9.9+0.38×103-× 2-1.01× 9.6/kloc-. 2.6×9.9 ×3 1+ ×+÷ ×36 ×38 13.5×27+ 13.5×72+ 13.5 1 .5×7.4+0.6× 150%+2÷ 5.3×+2.7×25% 0.67× 10. / kloc-0/-6.7 28×2 1.6-2.8× 16 5.6× 1.7+0.56×83