Question

What is the least common multiple of 10, 20 and 30?

• A. 10
• B. 30
• C. 60
• D. 120

Answer 1

The correct option is C 60

Multiples of 10 are 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, ... and so on.

Multiples of 20 are 20, 40, 60, 80, 100, 120, ... and so on.

Multiples of 30 are 30, 60, 90, 120, 150, 180, ... and so on.

The common multiples of 10, 20 and 30 are 60, 120, 180, ... and so on.

The least of these is called the LCM or the least common multiple of 10, 20 and 30.

$\therefore$ 60 is the LCM of 10, 20 and 30.