Highest Common Factors

What is the highest common factor of each pair of numbers? You will probably want some paper to work out on.
e.g. 48 and 60

48 = 2 x 24
48 = 2 x 2 x 12
48 = 2 x 2 x 2 x 6
48 = 2 x 2 x
2 x 2 x 3
60 = 2 x 30
60 = 2 x 2 x 15
60 =
2 x 2 x 3 x 5

The common factors are 2, 2 and 3.
So the HCF of 48 and 60 is 2 x 2 x 3 = 12

1. 6 and 8  
 
2. 12 and 18  
 
3. 30 and 24  
 
4. 36 and 27  
 
5. 56 and 42  
 
6. 72 and 48  
 
7. 54 and 36  
 
8. 63 and 84  
 
9. 75 and 105  
 
10. 64 and 80  
 

If you made any mistakes, have another go at those questions.

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