LCM = least common multiple
You are looking for the smallest positive number that is a shared multiple of both numbers.
For the first one, these are the multiples of each number:
10: 10, 20, 30, 40, 50, 60, 70, 80…
25: 25, 50, 75, 100, 125…
The smallest multiple between these two would be 50, answer #4.
Problem 2:
24: 24, 48, 72, 96…
36: 36, 72, 108, 144…
The smallest multiple is 72, which is answer #2
