Helpme123: What is the HCF of 120 and 42 and how do I find it out?
One good way is as follows.
Choose the smaller number which is 42
1*42=42 so 1 and 42 are factors and 42 is the biggest factor of 42. Does 42 go into 120? NO so we'll look for the next biggest factor of 42
2*21=42 so 2 and 21 are factors and 21 is the next biggest factor of 42. Does 21 go into 120? NO so we'll look for the next biggest factor of 42
3*14=42 so 3 and 14 are factors and 14 is the next biggest factor of 42. Does 14 go into 120? NO so we'll look for the next biggest factor of 42 (4 and 5 don't go into 42)
6*7=42 so 6 and 7 are factors and 7 is the next biggest factor of 42. Does 21 go into 120? NO so we'll look for the next biggest factor of 42
Since there is no numbers between 6 and 7 we have now found all the factors of 42 so the next biggest one must be 6
does 6 go into 120? YES
So 6 must be the Highest common factor.
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It might have been easier just to write down all the factors of 42 then put them in order and then look which ones go into 120 and select the biggest one.
1,42,2,21,3,14,6,7
1,2,3,6,7,14,21,42
The biggest one that goes into 120 is 6
So 6 must be the Highest common factor.
+118653 
