1. The properties of the division operation

2. Calculate fast 2×5= 4×5= 6×5= 8×5= 10×5= 10 100 20 200 30 300 40 400
20×5=
40×5=
60×5=
80×5=
100×5=
2×5= 4×5= 6×5= 8×5= 10×5= 10
100 20
200 30
300 40
400 50
500

3. 2×10= 4×10= 6×10= 8×10= 10×10= 20
2×25=
4×25=
8×25=
10×25= 50 40
100 60
200 80
100
250

4. The children went in 5 groups to plant trees
The children went in 5 groups to plant trees. There are 2 children in each group.
They planted 30 trees in total.
Q: How many trees are they planted per person?
30÷5÷2
30÷5÷2
=6÷2
=30÷（5×2）
=30÷10 =3 =3 =
30÷5÷2
30÷（5×2）

5. Do the calculations below have the same answer? Please try!
100÷25÷4
100÷(25×4)
18÷3÷2
18÷(3×2)
What do you find?
a÷b÷c=a÷(b×c) b≠0,c≠0

6. Fill the sign of operation in the circle
56÷ 7÷ 8＝ （ ）
＝15 ÷(3×5）
÷ 6＝24 ÷( ）

7. Fill the right number in the box
30÷ ÷ ＝30 ÷(2 ×5)
48÷( ×3)＝ ÷4 ÷3

8. Is it right? Can you correct their working? 14÷（2×7 ） ＝14÷2×7 ＝7×7 ＝49
What do you think?
Can you correct their working?

9. True or false × × √ （1）100÷（25×4）＝100÷25×4 （ ） （2）40÷（4×5）＝40÷4×5 （ ）
（1）100÷（25×4）＝100÷25×4 （ ） ×
（2）40÷（4×5）＝40÷4× （ ）
(3) 54÷（3×3）=54 ÷3 ÷ （ ） √

10. Can all formulae be calculated faster by using today's knowledge?
Which one is faster?
140÷7÷ ÷（7×4）
What do you find?
Can all formulae be calculated faster by using today's knowledge?

11. Look at the numbers carefully! Tell me about your findings.
100÷25÷4=100÷(25 ×4）
15÷ 3 ÷5＝15 ÷(3×5）
24÷ 4 ÷6＝24 ÷(4×6）

12. Who can calculate these faster?
1200÷25÷4 680÷17÷4