The most complete method classification of simple algorithms in primary school mathematics

The most complete method classification of simple algorithms in primary school mathematics;

1, borrow borrowing 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.

In the exam, when you see that 998,999 or 1.98 is close to a very easy-to-calculate integer, you often use the borrowing method.

For example:

9999+999+99+9

=9999+ 1+999+ 1+99+ 1+9+ 1—4

2. Split method

As the name implies, the splitting 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, 2 and 2.5, 4 and 2.5, 8 and 1.25. Be careful not to change the size of the number when splitting.

For example:

3.2× 12.5×25

=8×0.4× 12.5×25

=8× 12.5×0.4×25

3. Additive associative law

Pay attention to the law of additive association

The application of (A+B)+C = A+(B+C) makes the operation easier by changing the position of the addend.

For example:

5.76+ 13.67+4.24+6.33

=(5.76+4.24)+( 13.67+6.33)

3. Distribution laws of division and multiplication

This method needs to master the distribution rules of division and multiplication flexibly. When you see that 99, 10 1 9.8 is close to an integer, you should first consider division.

For example:

34×9.9=34×( 10-0. 1)

4. Use benchmark number

In several kinds of series, find a more eclectic number to represent this series. Of course, remember that the selection of this number should not deviate too far from this series.

For example:

2072+2052+2062+2042+2083

=(2062 X5)+ 10- 10-20+2 1

5, using the formula method

(1) addition:

Commutative law, a+b=b+a,

Law of association, (a+b)+c=a+(b+c).

(2) The nature of subtraction:

a-(b+c)=a-b-c，

a-(b-c)=a-b+c，

a-b-c=a-c-b，

(a+b)-c=a-c+b=b-c+a。