Answer:
To find the LCM you must find all factors of the numbers, and then multiply all the factors together including the ones that are not shared among the numbers.
For example,
Factors of 10: 2×5
Factors of 30: 2×3×5
LCM of 10 and 30: 2×3×5 = 30
However do note not to multiply a factor more than once if it is shared among two numbers.
