multiply by 3 and 4
multiply by 5 and 10
multiply by 6 and 7
find the unknown number
repeat addition
100

3 x 4 =

12

100

5 x 3 =

15

100

6 x 2 =

12

100

n x 8 =16

n =2

100

3 + 3 + 3 =

3 x 3 = 9

200

4 x 5 =

20

200

10 x 4 =

40

200

3 x 7 =

21

200

4 x n =28

n = 7

200

7 + 7 + 7 = 

3 x 7 = 21

300

3 x 6 =

18

300

5 x 6 =

30

300

6 x 4 =

24

300

6 x 6 = n

n = 36

300

10 + 10 + 10 + 10 =

4 x 10 = 40

400

3 x 8 =

24

400

10 x 8 =

80

400

6 x 7 =

42

400

n / 7 = 4

n = 28

400

8 + 8 + 8 + 8 = 

4 x 8 = 32

500

4 x 9 =

36

500

5 x 9 =

45

500

8 x 7 =

56

500

8 x n = 48

n = 6

500

9 + 9 + 9 =

3 x 9 = 27

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