Example 4
Walkthrough 1
Find the lowest common multiple and the highest common factor of 6 and 9.
Summary
Multiples of 6: 6, 12, 18, 24, 30, 36, ...
Multiples of 9: 9, 18, 27, 36, ....
LCM = 18
Factors of 6: 1, 2, 3, 6
Factors of 9: 1, 3, 9
HCF = 3
Many numbers have an even number of factors.
For example, the factors of 20 are:
1 and 20, 2 and 10, 4 and 5
Square numbers have an odd number of factors.
For example, the factors of 16 are:
1 and 16, 2 and 8, 4
Since 6 and 9 do not have any common factors other than 1, their highest common factor is 1. And since both 6 and 9 have a common multiple of 18, their lowest common multiple is 18.