1. Commutative law

2. Story:
Monkey king and peaches
Arithmetic
Calculation
Operation
How do you feel?
Explain it in maths

3. Find similarities and differences
3+4= =7
3+4=4+3

4. Task 1
8+18=26
18+8=26
8+18=18+8
How many cans of fruit juice in all?

5. Task 1
Can you give other examples like this?

6. commutative law of addition
Task 1
Add two numbers, exchange the place of the numbers being added and their sum remains the same.
commutative law of addition

7. Task 1
Algebraically:
a + b = b + a

8. Game Time
I say 1+2
you say 2+1

9. follow-up exercises 214 y ☆ △ 1 1 5 5 ……
Fill in the blanks by using commutative law of addition
256＋214=           ＋256
X+Y=          ＋X
△+☆=          ＋
十 367=367 ＋      
214 y ☆ △ 1 1 5 5 ……
Add two numbers, exchange the place of the numbers being added and their sum remains the same.

10. Task 2
Does any other operation have commutative law?
Show examples of each operations

11. commutative law of multiplication
Task 2
Multiply two numbers. Exchange the places of factors and their product remains the same.
commutative law of multiplication

12. Can you draw a diagram to show it?
Task 2
Algebraically:
a × b = b × a
Can you draw a diagram to show it?

13. 34×71= × 45× =55× ×▲= ×■ × =C×D 71 34 55 45 ■ ▲ D C
Fill in the blanks by using
commutative law of multiplication
34×71= × × =55×
×▲= ×■ × =C×D 71 34 55 45 ■ ▲ D C
Multiply two numbers. Exchange the places of factors and their product remains the same.

14. EXERCISE

15. 1、true or false： 56+38=83+56 is using the commutative
law of addition.（ ）
2×3=1×6 is using commutative law of
multiplication. （ ）
(3) A×B=B+A。（ ）
(4) □+△+○= □+○+△。（ ） × × × √

16. 2、Fill in the blanks by using commutative law
52×（ ）=141 ×（ ）
=55+（ ）+87
☆+（ ）=●+（ ）
25×18×4=（ ）×（ ）×（ ）
△×（ ）×★=（ ）×★×☺
141 52 45 ● ☆ 25 4 18 ☺ △

17. 3、 QUICK CACULATION (STEP BY STEP)
28＋45＋72      62＋38＋123  （151+33)
8×23× ×43×40 = = =
=251 =
=100+45
=145 =
=100+38
=138
=25×40×43
=1000×43
=43000
=8×125×23
=1000×23
=23000

18. 4、Solve the problem
Miss White bought gifts for the class, the class has 25 students and each present need 12 pounds, how much does Miss White pay altogether?
25×12
=25×4×3
=100×3
=300

19. 5. Alex is going to have a party at home
5. Alex is going to have a party at home. His Mum bought 2 dozens of coke, 32 apples, 24 bananas and 8 peaches. How many fruits did she buy?

20. Try your best:
John and Lucy are calculating
98 ＋ 998 ＋ 98 ＋ 2 × 3,
John find the correct answer right away. Can you?

21. Summary
What have you learned today?