Fourth grade simple operation multiplication and division method: multiplication exchange law, multiplication association law, multiplication distribution law, division association law, division exchange law.

1, multiplication commutator: 25× 56× 4 = 25× 4× 56 =100× 56 = 5600.

2. Multiplicative associative law: 25×125× 4× 8 = (25× 4 )× (125× 8) =100×1000.

3. Multiplicative distribution law: 25× (40+4) = 25× 40+25× 4 =1100; 135× 12— 135×2= 135×( 12—2)= 135× 10= 1350。

4. Division law: 3200 ÷ 25 ÷ 4 = 3200 ÷ (25× 4) = 3200 ÷100 = 32.

5. Division commutative law: 256-58+44 = 256+44-58 = 300-58 = 242; 250÷8×4=250×4÷8= 1000÷8= 125。

Fourth grade multiplication learning skills

Multiplication of two numbers within 20: Multiply two numbers within 20, add the single digits of one number with another number, multiply by 10, and add the product of two mantissas to get the desired number. For example, 12× 13 = 156. The calculation program is to add the mantissa 2 of 12 to 13, and 13 plus 2 equals 15,/kloc-0. Another example is:17×18 = (17+8 )×10+7× 8 = 306.

Head-to-tail complementary multiplication: formula: head plus 1 head multiplied by head and tail multiplied by tail. Multiply two tens, the first one is the same as the last one, but the last ten are complementary. The calculation method is: add 1 to the head, then multiply the front product by the head and multiply the rear product by the tail. When two products are connected, it is the required number. Such as 26× 24 = 624. The calculation program is: the head of the multiplicand 26 plus 1 equals 3, and then the head is multiplied by the head, which is 3 × 2 = 6, and the tail is multiplied by 6 × 4 = 24, and the connection is 624.