1. The greatest common factor of 8 and 20 is

2. The common factor of 9 and 15 is

3. The common factor of 4 and 15 is

4. Which of the following pairs of number are not co-prime?

5. Which of the following pairs of number are co-prime?

6. The greatest common factor of 4, 8 and 12 is

7. The greatest common factor of 5, 15 and 25 is

8. The common factor of 3, 4 and 9 is

9. The greatest common factor of 75,60 and 210 is

10. The smallest common factor of 4, 12 and 16 is