The simple calculation is enjoyment. Observe carefully and find the features.

Continuous addition, pairing. Ride in a row and find friends.

Continuous subtraction, subtraction, addition. Continuous division, by product.

Subtract sum, and you can even subtract it. Divide by the product, you can divide by it.

Multiply and difference, multiply separately. Add and subtract, don't panic,

The same factor, put forward, different factors, put in brackets.

At the same level, interchangeable. Special number, cleverly split.

Reasonable, I can do it.

Seven common simple operation methods

1 method 1: signed shift 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"

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)

2 Method 2: Constraint method

(A) bracket method

1. When adding parentheses, 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.

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.

(2) Method of removing brackets

1. In addition and subtraction, when removing brackets, add a plus sign and a minus sign before the brackets. When the brackets are deleted, the symbol will be changed (the original addition in brackets will now be reduced; It used to be negative, but now it is positive. )。

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 original brackets is now divided; It used to be division, but now it's multiplication. )。

3 Method 3: Multiplication and Distribution Law

1. allocation method

Parentheses are addition or subtraction operations, multiplied by another number. Pay attention to distribution.

Example: 8×(3+7)

=8×3+8×7

=24+56

=80

Step 2: Extract common factors.

Pay attention to the extraction of the same factor.

Example: 9×8+9×2

=9×(8+2)

=9× 10

=90

3. Pay attention to the structure to make the formula conform to the conditions of multiplication and division.

Example: 8×99

=8×( 100- 1)

=8× 100-8× 1

=800-8

=792

4 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.

For example: 9999+999+99+9

=( 10000- 1)+( 1000- 1)+( 100- 1)+( 10- 1)

=( 10000+ 1000+ 100+ 10)-4

= 1 1 1 10-4

= 1 1 106

5 Method 4: 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.

For example: 32× 125×25

=4×8× 125×25

=(4×25)×(8× 125)

= 100× 1000

= 100000

6 Method 5: Clever change from division to multiplication

Dividing by a number is equal to multiplying the reciprocal of this number.

7 Method 6: Split Term Method

Fraction splitting refers to splitting the items in the fraction formula so that the split items can be offset before and after. This splitting calculation is called splitting method. The common splitting method is to split a number into the sum or difference of two or more digital units.

When you encounter the calculation problem of cracked items, you should pay attention to:

1. continuity

2. Homomorphism

Calculation method: head and tail reduction. In addition to tolerance.