Method 1: signed moving method

When a calculation problem only has the same level operation (only multiplication and division or only addition and subtraction) without brackets, we can "move with signs"

Method 2: Constraint method

1, parenthesis method:

(1) When adding parentheses for addition and subtraction, there is a plus sign in front of the parentheses, a constant sign in the parentheses, a minus sign in front of the parentheses and a sign in the parentheses. For example: 23+19-9 = 23+(19-9); 33-6-4=33-(6+4)。

(2) When the multiplication and division method is bracketed, the multiplication symbol is in front of the bracket, the constant symbol is in the bracket, the division symbol is in front of the bracket, and the symbol is changed in the bracket. For example: 2× 6 ÷ 3 = 2× (6 ÷ 3); 10÷2÷5= 10÷(2×5)。

2, to support method:

(1) In addition and subtraction, when the brackets are removed, a plus sign is added before the brackets and a minus sign is added before the brackets. When the brackets are deleted, the symbol will change (the original addition in brackets is now reduced; It used to be negative, but now it will be positive. For example:17+(13-7) =17+13-7; 23-( 13-9)=23- 13+9; 23-( 13+5)=23- 13-5。

(2) When removing the brackets in the multiplication and division method, add a multiplication sign in front of the brackets, a constant sign after the brackets, and a division sign after the brackets (the multiplication in the brackets is now divided; It used to be division, but now it's multiplication. For example:1× (6 ÷ 2) =1× 6 ÷ 2; 24÷(3×2)=24÷3÷2; 24÷(6÷3)=24÷6×3。

Method 3: Multiplication and distribution law

Distribution method: Add and subtract in brackets, and multiply by another number. Pay attention to distribution. For example: 8× (5+11) = 8× 5+8×11.

Common factor extraction method: pay attention to the extraction of the same factor. For example: 9×8+9×2=9×(8+2).

Method 4: Rounding method

See the name, and you will know the meaning of this method. When using this method, we need to pay attention to observation and find the law. Also pay attention to paying back the money. If you borrow it, it is not difficult to borrow it again.

Method 5: Split method

Split method is to split a number into several numbers for the convenience of calculation. This requires mastering some "good friends", such as: 2 and 5, 4 and 5, 4 and 25, 8 and 125. Be careful not to change the size of the number when splitting.