1, additive commutative law: Two numbers are added to exchange the position of addend, and the sum is unchanged.
2. Law of additive combination: When three numbers are added, the first two numbers are added first, or the last two numbers are added first, and then the third number is added, and the sum remains unchanged.
3. Multiplication and exchange law: when two numbers are multiplied, the position of the exchange factor remains unchanged.
4. Multiplication and association law: When three numbers are multiplied, the first two numbers are multiplied, or the last two numbers are multiplied first and then the third number, and their products are unchanged.
5. Multiplication and distribution law: When two numbers are multiplied by the same number, you can multiply the two addends by this number respectively, and then add the two products, and the result remains unchanged. Such as: (2+4) × 5 = 2 × 5+4 × 56. The essence of division: in division, the dividend and divisor are expanded (or reduced) by the same multiple at the same time, and the quotient remains unchanged.
O is divided by any number that is not O. Simple multiplication: the multiplicand and the end of the multiplier are multiplied by O. You can multiply 1 before o first, and zero does not participate in the operation, and add a few zeros at the end of the product.
Extended data:
Six skills of simple operation in primary school mathematics;
1, using the law of additive combination for simple calculation.
(a+b)+c=a+(b+c)
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
2. Simple calculation by using the law of multiplicative association: This kind of problem often includes multiplication between special numbers.
(a×b)×c=a×(b×c)
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
3. Use the multiplication and division method for simple calculation: (Do not rush to calculate this kind of problem, first analyze the special relationship between numbers. That is to say, we should observe carefully first and find the trick to do the problem. )
(a+b)×c=a×c+b×c
(a-b)×c=a×c-b×c
Example 5, (2.5+ 12.5) × 40
=2.5×40+ 12.5×40
= 100+500
=600
Example 6, 3.68× 4.79+6.32× 4.79
=(3.68+6.32)×4.79
= 10×4.79
=47.9
Example 7.26.86× 25.66-16.86× 25.66
=(26.86- 16.86)×25.66
= 10×25.66
=256.6
4. Split the logarithm by addition, subtraction, multiplication and division, and then make a simple calculation by multiplication and division:
Example 8, 34×9.9
=34×( 10-0. 1)
=34× 10-34×0. 1
=340-3.4
=336.6
Example 9,57×101
=57×( 100+ 1)
=57× 100+57× 1
=5757
For example, 10, 7.8× 1. 1.
=7.8×( 1+0. 1)
=7.8× 1+7.8×0. 1
=7.8+0.78
=8.58
Example 1 1, 25×32
=25×4×8
= 100×8
=800
5. Even reduction and division
a-b-c=a-(b+c)a÷b÷c=a÷(b×c)
Example12,56.5-3.7-6.3
=56.5-(3.7+6.3)
=56.5- 10
=46.5
Example13,32.6 ÷ 0.4 ÷ 2.5
=32.6÷(0.4×2.5)
=32.6÷ 1
=32.6
6. Simple calculation that requires deformation: To do this kind of problem, you should observe first, find out the law, and then do simple calculation after deformation.
For example,14,86.7× 0.356+1.33× 3.56.
=8.67×3.56+ 1.33×3.56
=(8.56+ 1.33)×3.56
= 10×3.56
=35.6