40

80

40

80

40÷2

80÷2

20

40

20÷2

40÷2

10

20

10÷2

20÷2

5

10

5÷5

10÷5

1

2

or

40

80

2 × 2 × 2 × 5

2 × 2 × 2 × 2 × 5

1

2

or

Common Divisors for 40 and 80 are: 2, 2, 2 and 5

Greatest Common Divisor = 2 × 2 × 2 × 5 = 40

40÷40

80÷40

1

2

See 1/2 as a percent