Least Common Multiple means we need to know the multiplication tables of two or more numbers when we're asked to discover the smallest or least multiple they have in common.

For example:

The multiples of 5 are: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50...
The multiples of 9 are: 9, 18, 27, 36, 45 ...

The least common multiple of 5 and 9 is 45.

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Another example:

The multiples of 6 are: 6, 12, 18, 24, 30, 36, 42, 48...
The multiples of 9 are : 9, 18...

The least common multiple of 6 and 9 is 18.

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And one more example:

The multiples of 18 are: 18, 36, 54, 72, 90...
The multiples of 24 are: 24, 48, 72...

The least common multiple of 18 and 24 is 72.