## Tutoring: what is it and how to calculate the least common multiple LCM of integer numbers

60 is a common multiple of the numbers 6 and 15, because 60 is a multiple of 6 and is also a multiple of 15. But there is also an infinite number of common multiples of 6 and 15.

#### If "v" is a multiple of "a" and "b", then all the multiples of "v" are also multiples of "a" and "b".

Common multiples of 6 and 15 are: 30, 60, 90, 120... Among them, 30 is the lowest and we say that 30 is the **least common multiple, or the lowest common multiple, or the smallest common multiple** of 6 and 15, abbreviated as **LCM**.

#### If e = LCM (a; b), then "e" contains all the prime factors involved in the prime factorizations of both "a" and "b", by the highest powers (exponents).

Based on this rule we can calculate the least common multiple, LCM, of the three numbers in the example below:

- 40 = 2
^{3}× 5 - 36 = 2
^{2}× 3^{2} - 126 = 2 × 3
^{2}× 7 - LCM (40; 36; 126) = 2
^{3}× 3^{2}× 5 × 7 = 2,520