Exercise 3.2b (casting out of nines method)

Exercise 3.2b

1. Circle the correct multiplication fact (by using casting out nine method).

a) 312 × 36 = 11232

b) 723 × 24 = 17508

c) 132 × 43 = 5676

a) 312 × 36 = 11232

312 × 36 = 11232

3+1+2 x 0 = 0

6 x 0 = 0

0 = 0

It is correct multiplication fact.

b) 723 × 24 = 17508

723 × 24 = 17508

3x6= 7+5+0

18 = 12

9 ≠ 3

It is not correct multiplication fact.

c) 132 × 43 = 5676

132 × 43 = 5676

1+3+2 x 4+3 = 5 + 6 + 7 + 6

6 x 7 = 24

42 = 24

6 = 6

It is correct multiplication fact.

2. Circle the correct division fact (by using casting out nine method).

a) 728 ÷ 4 = 182

b) 1580 ÷ 20 = 78

c) 7785 ÷ 9 = 865

a) 728 ÷ 4 = 182

728 ÷ 4 = 182

8 ÷ 4 = 2

8 = 2 x 4

It is correct division fact.

b) 1580 ÷ 20 = 78

1580 ÷ 20 = 78

[1 + 5 + 8] ÷ 2 = 7 + 8

14 ÷ 2 = 15

5 = 15 x 2

5 = 30

5 = 3

It is not the correct division fact

c) 7785 ÷ 9 = 865

7785 ÷ 9 = 865

7+ 7 + 8 + 5 = 8 + 6 + 5

27 ÷ 9 = 19

9 ÷ 9 = 10

9 = 1 x 9

9 = 9

It is the correct division fact