1. Review: 3 2s 2 3s 4 2s 2 4s 2+2+2 3+3 2+2+2+2 4+4 groups
( ) in each group
3 2s
2+2+2
2 3s
3+3
4 2s
2 4s
4+4

3. Exploration
How many groups of 3?
1 group of 3.

4. Exploration
3 children in each boat.
How many groups of 3？
2 groups of 3
How many children are rowing?
3+3=6

5. Exploration
Repeated addition
Look at the addition sentences,
What do you notice?
How many groups of 3？
6 groups of 3
How many children are rowing?
=18

6. How many children are rowing?
Exploration
The number sentence for 10 groups of 3
is very long. What is a easier way of
writing the number sentence?
How many groups of 3？
10 groups of 3
How many children are rowing?
=30

7. 10 × 3 = 30 Exploration How many groups of 3？ 10 groups of 3
When we add the same things lots of times, it is easier for us to multiply.
How many groups of 3？
10 groups of 3
How many children are rowing?
=30
10 × 3 = 30
10 times 3 equals 30.
There are boats, children in each boat.
There are children altogether. 10 3 30

8. Moving from
addition
to multiplication

9. Do you know?
William Oughtred
The sign “×” was first used by an English mathematician William Oughtred in Because the multiplication is a special kind of addition, Oughtred used the addition sign.

10. 5 4s How many children are there in the cups altogether?
Look at the picture carefully.
5 4s
Repeated addition
number sentence：____________________________
Multiplication × =
, children in one cup, altogether.
=20 5 4 20 5 4 20

11. 6 2s × = 2+2+2+2+2+2=12 6 2 12 6 2 12 How many children
are there in the cars altogether？
6 2s
Repeated addition
number sentence：_______________________________
Multiplication × =
， children in one car, altogether.
=12 6 2 12 6 2 12

12. 1+1+1+1+1+1+1+1+1+1+1+1=12 12 × 1=12 2+2+2+2+2+2=12 6 × 2=12
multiplication number sentence:
=12
12 × 1=12
=12
6 × 2=12
=12
4× 3=12
4+4+4=12
3× 4=12
6+6=12
2× 6=12 1 2 3 4 6

13. True or False
(1) =3 ×2 F
(2) =4 ×8 T
(3) 6 5s= F

14. Summary Repeated addition number sentences can be transformed into
multiplication number sentences.

15. Challenge
=____×____

16. Challenge 4 10
=____×____ 10

17. Challenge 5 5 5 8 5
=____×____