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Mixed operation of addition, subtraction, multiplication and division in grade two
According to the different characteristics of the formula, the calculation process can be simplified or the results can be obtained directly by using the synthesis and decomposition of numbers, various operation rules, properties or their special relationships. This simple and fast operation is called simple calculation.

This requires students to have a thorough understanding and correct application of the nature, laws and rules they have learned before making simple calculations. In other words, this knowledge can simplify the calculation process, and at the same time use the skills of rounding, splitting, transformation and splitting to achieve the purpose of fast calculation.

Extended data

1. Make a simple calculation by using the additive combination law.

(A+B)+C = A+(B+C) or a+b+c+d=(a+c)+(b+d)

For example 1, 5.76+ 13.67+4.24+6.33.

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

= 10+ 10

=20

Example 2, 37.24+23.79- 17.24

=37.24- 17.24+23.79

=20+23.79

=43.79

Second, use the law of multiplicative association to make simple calculations: this kind of problems often include multiplication between special numbers.

(a×b)×c=a×(b×c)

Multiplication between special numbers:

25×4= 100 125×8= 1000 25×8=200 125×4=500

Example 3,4× 3.78× 0.25

=4×0.25×3.78

= 1×3.78

=3.78

Example 4: 125×246×0.8

= 125×0.8×246

= 100×246

=24600

2.5×0. 125×8×4, etc. If division is also applicable, it is still divided into multiplication. Such as: 8.3×67÷8.3÷6.7, etc.

Thirdly, the multiplication and distribution law is used for simple calculation:

(a+b)×c=a×c+ b×c

(a-b)×c=a×c- b×c