1. Distributive law of multiplication

2. A.（6+4）×5 6×5+4×5 B.（8+12）×4 8×4+12×4 C. 10×（7+3） 10×7+10×3 = = =
1. First find the value of two number sentences of each set ,then talk about what do you find out?
A.（6+4）× ×5+4×5
B.（8+12）× ×4+12×4
C. 10×（7+3） ×7+10×3 = = =

3. 70m 40m 10m Please find: Example 1:
There is a rectangular playground in a primary school ,it is 70 meters long and 40 meters wide.
After the expansion, it will be increased by 10 meters wide.
the area of the playground
after expansion .
Please find:
70m
40m
Hint:
The area of a rectangle = length ×width
10m

4. =50 ×70 =3500（m2） =2800+700 =3500（m2） Example 1:
There is a rectangular playground in a primary school ,
it is 70 meters long and 40 meters wide.
After the expansion, it will be increased by 10 meters wide. Please find the area of the playground after expansion ?
Way1:（40+10） × 70
=50 ×70
=3500（m2）
70m
40m
10m
Way2: 40×70+10×70 =
=3500（m2）
How do you
think about ?

5. = （6+4）×5 = 6×5+4×5 Way 1 Way 2 （40+10)× 70 40×70+10×70 = 2800+700
What do you find out?
Hint: on the left of the equals sign is……
on the right of the equals sign is……
The answers on both side are ……
Way 1
（40+10)× 70
Way 2
40×70+10×70 =
=50 ×70
=3500（m2） =
=3500（m2）
（6+4）× = ×5+4×5
（8+12）×4 = 8×4+12×4
10×（7+3） = ×7+10×3

6. Can you find more examples like this？
（40+10）× = 40× ×70
( ＋ )× = × ＋ ×
Distributive law of multiplication.
The sum of two numbers multiplied by another number. We can multiplied the two addends by the number respectively and then add two products. The result remains the same.

7. (1)（93＋28）×11= × ＋ ×11 11 (2) 20×（80－10）=20× －20× (3) ◆ ×★+●×★=（ + ）×
Distributive law of multiplication.
The sum of two numbers multiplied by another number. We can multiplied the two addends by the number respectively and then add two products. The result remains the same.
（a + b）×c=a×c + b×c
1.Fill in the blanks according to distributive law of multiplication.
(1)（93＋28）×11= × ＋ ×11
(2) 20×（80－10）=20× －20×
(3) ◆ ×★+●×★=（ ）× 11

8. × × × Distributive law of multiplication.
The sum of two numbers multiplied by another number. We can multiplied the two addends by the number respectively and then add two products. The result remains the same.
（a + b）×c=a×c + b×c
2 .Judge but no calculation ,then give the reason.
(Show them with “√”or“×”)
（a）（22－17）×35=22×35－22× （ ）
（b） 78×91＋91×25= 78＋25 × （ ）
（c） 8×（11×9）=8×11×8× （ ） × × ×

9. （a + b）×c=a×c + b×c （1） 125×（8+1） （2）17×148-17×48 =125×8+125×1
3. Solve each problem below with the distributive law of multiplication
（1） 125×（8+1） （2）17×148-17×48
=125×8+125×1
=17×( ) =
=17×100
=1700
=1125
Use the distributive law of multiplication can make the calculation simple.

10. 4.Do the simple calculation with the laws
you’ve learned.
25×24

11. Thank you!