Finding HCF by using prime factors

What is the prime factorisation of 54?

•  $2\times3\times3\times3$  

•  $2\times2\times3\times3$  

•  $6\times3\times3$  

•  $2\times3\times4$  

What is the prime factorisation of 108?

•  $2\times2\times3\times3\times3$  

•  $2\times2\times3\times3$  

•  $2\times2\times3\times3\times5$  

•  $2\times3\times3\times3\times7$  

 $54=2\times3\times3\times3$  
 $108=2\times2\times3\times3\times3$  
Using prime factors, find the HCF of 54 and 108.

 $60=2\times2\times3\times5$  
 $90=2\times3\times3\times5$  
Using prime factors, find the HCF of 60 and 90.

 $42=2\times3\times7$  
 $70=2\times5\times7$  

Find the HCF of 42 and 70.

 $105=3\times5\times7$  

 $30=2\times3\times5$  

Find the HCF of 105 and 30.

What is the HCF of 45 and 180?

What is the HCF of 36 and 42?

What is the HCF of 32 and 48?

What is the HCF of 36 and 45?