HCF
Q. Find the highest common factor of 12 and 15.
A. Write out all of the factors, that is all of the numbers that go exactly into each number and make 2 parallel lists.
The factors of 12 are: 1, 2, 3, 4, 6 and 12
The factors of 15 are: 1, 3, 5 and 15
The numbers that appear in each list are 1 and 3, but the largest is number 3 which is therefore the highest common factor.
Q. Using prime factorisation and a Venn diagram representation, find the HCF and LCM of 15, 21 and 28:
A. Using prime factor trees (not shown here), look for the primes of each number:
As there is NO HCF shown, the declared HCF would be 1, as ANY number has 1 as a common factor.
The LCM in this case is:
Q. Using prime factorisation and a Venn diagram representation, find the HCF and LCM of 36, 58 and 86:
A. Using prime factor trees (not shown here), look for the primes of each number:
The HCF in this case is 2
The LCM in this case is:
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