1. Highest Common Factors – Listing – Bingo Method
Students should choose nine answers from the grid and place them
randomly into a 3x3 square in their book.
You may want to pause your display and choose questions
according to difficulty during the game.
Depending on time, students could win with
a line, an X, or a ‘full house’ (all).

2. Printing To print handouts from slides -
Select the slide from the left. Then click:
File > Print > ‘Print Current Slide’
To print multiple slides -
Click on a section title to highlight all those slides,
or press ‘Ctrl’ at the same time as selecting slides to
highlight more than one. Then click:
File > Print > ‘Print Selection’
To print double-sided handouts -
Highlight both slides before using ‘Print Selection’.
Choose ‘Print on Both Sides’ and ‘Flip on Short Edge’.

3. Highest Common Factors with Lists
BINGO! 45 54 23 82 37 12 76 25 91
Finding
Highest Common Factors with Lists

4. Choose your numbers… 9 2 3 8 6 5 4 7 1
You may pick a number more than once,
but you may only cross them off one at a time.
Draw a 3x3 grid in your book.

5. What is the highest common factor of
24 & 16?
Factors of 24: 1, 2, 3, 4, 6, 8, 12
Factors of 16: 1, 2, 4, 8, 16 8

6. What is the highest common factor of
12 & 8?
Factors of 12: 1, 2, 3, 4, 6, 12
Factors of 8: 1, 2, 4, 8 4

7. What is the highest common factor of
11 & 9?
Factors of 11: 1, 11
Factors of 9: 1, 9 1

8. What is the highest common factor of
16 & 8?
Factors of 16: 1, 2, 4, 8, 16
Factors of 8: 1, 2, 4, 8 8

9. What is the highest common factor of
18 & 15?
Factors of 18: 1, 2, 3, 6, 9, 18
Factors of 15: 1, 3, 5, 15 3

10. What is the highest common factor of
20 & 15?
Factors of 20: 1, 2, 4, 5, 10, 20
Factors of 15: 1, 3, 5, 15 5

11. What is the highest common factor of
14 & 18?
Factors of 14: 1, 2, 7, 14
Factors of 9: 1, 2, 3, 9 2

12. What is the highest common factor of
18 & 12?
Factors of 18: 1, 2, 3, 6, 9, 18
Factors of 12: 1, 2, 3, 4, 6, 12 6

13. What is the highest common factor of
20 & 12?
Factors of 20: 1, 2, 4, 5, 10, 20
Factors of 12: 1, 2, 3, 4, 6, 12 4

14. What is the highest common factor of
15 & 18?
Factors of 15: 1, 2, 3, 5, 15
Factors of 18: 1, 2, 3, 6, 9, 18 3

15. What is the highest common factor of
25 & 20?
Factors of 25: 1, 5, 25
Factors of 20: 1, 2, 4, 5, 10, 20 5

16. What is the highest common factor of
24 & 18?
Factors of 24: 1, 2, 3, 4, 6, 8, 12, 24
Factors of 18: 1, 2, 3, 6, 9, 18 6

17. What is the highest common factor of
21 & 28?
Factors of 21: 1, 2, 3, 7, 21
Factors of 28: 1, 2, 4, 7, 14, 28 7

18. What is the highest common factor of
27 & 36?
Factors of 27: 1, 2, 3, 9, 27
Factors of 36: 1, 2, 3, 4, 6, 9, 12,
18, 36 9

19. What is the highest common factor of
32 & 40?
Factors of 32: 1, 2, 4, 8, 16, 32
Factors of 40: 1, 2, 4, 8, 10, 20, 40 8

20. What is the highest common factor of
16 & 28?
Factors of 16: 1, 2, 4, 8, 16
Factors of 28: 1, 2, 4, 7, 14, 28 4

22. tom@goteachmaths.co.uk Questions? Comments? Suggestions?
…or have you found a mistake!?
Any feedback would be appreciated .
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