Summary of knowledge points of multiplication and distribution law
Knowledge points:
1, multiplication and distribution law: the sum (or difference) of two numbers is multiplied by a number, and two addends (or minuend and minuend) can be multiplied by this number respectively. After adding (or subtracting) two products, the result remains the same. Use letters to represent numbers: (a+b)×c=a×c+b×c or (a-b) × c = a× c-b× c.
Supplementary knowledge points:
2. Features of the formula: The original symbols of the formula are generally ×,+(-) and ×; There are the same factors in the two multiplication formulas; The other is that the sum (or difference) of two different factors can basically add up to a whole number of ten, one hundred and one thousand.
3. 102×88 and 99× 15 are characterized by multiplying two numbers, rewriting one of them as the sum (or difference) of integer ten, integer hundred, integer thousand and a number, and then applying the laws of multiplication and distribution to make the operation simple.
Knowledge points of multiplicative associative law
Knowledge points:
1, multiplication and association law: when three numbers are multiplied, the first two numbers are multiplied by the third number, or the last two numbers are multiplied by the first number, and their products are unchanged. Expressed in letters: (a×b)×c=a×(b×c).
2. Timing of use: When several numbers are multiplied, if two of them are multiplied into integer ten, integer hundred and integer thousand, the multiplicative commutative law and multiplicative associative law can be applied. Multiplication association law can change the order of multiplication operations. Numbers such as; 25 and 4, 50 and 2, 125 and 8, 50 and 4,500 and 2, etc.
Exercise questions:
Type 1: (Note: Numbers outside brackets must be multiplied by two numbers in brackets respectively, and then the products are added)
(40+8)×25 125×(8+80)
36×( 100+50)24×(2+ 10)
86×( 1000-2) 15×(40-8)
Type 2: (Note: the same factor in two products can only be written once)
36×34+36×66 75×23+25×23
63×43+57×6393×6+93×4
325× 1 13-325× 13 28× 18-8×28
Type 3: (hint: take 102 as100+1; 8 1 is regarded as 80+ 1, and then the multiplication distribution law is used)
78× 102 69× 102
56× 10 1 52× 102
125×8 1 25×4 1
Type 4: (hint: take 99 as100-1; 79 as 80- 1, and then use the multiplication distribution law)
3 1×99 42×9829×99
85×98 125×7925×39
Fifth: (hint: take 56 as 56× 1, and then use the multiplication distribution law)
83+83×9956+56×99
99×99+9975× 10 1-75
125×8 1- 1259 1×3 1-9 1
A. What are the courses of primary education?
Pedagogy, psychology, logic, Mandarin, teachers' oral English, teaching design, etc.
1, pedagogy<