Write down multiples of each number until you find the first common multiple:

The multipliers of 4 are: 4, 8, 12, 16, 20, 24, 28, 32, . . .

The multipliers of 7 are: 7, 14, 21, 28, 35, . . .

The multipliers of 1 are: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, . . .

We can see that:

LCM( 4, 7, 1 ) = 28

This solution can be visualized using a Venn diagram.

The LCM is equal to the product of all the numbers on the diagram.