Greatest Common Factor & Least Common Multiple

A factor of a number is a whole number that, when multiplied by another whole number, equals the original number. For example, 4 and 2 are factors of 8 because 4 × 2 = 8.

10: 1, 2, 5, 10. 8: 1, 2, 4, 8. 2 is a common factor.

A multiple of a number, n, is a number that I can find by multiplying n by a whole number.

4: 4, 8, 12, 16, 20, 24, …; 6: 6, 12, 18, 24, 30, 36, …; both lists have 12 and 24.

I could color in squares on a number chart. I count skip count on a number line.

The GCF of two numbers is the greatest number that is a factor of both numbers.

Yes, two numbers may have no factors in common except 1, like 2 and 3.

The LCM of two numbers is the least number that is a multiple of both numbers.

When I look at the two lists of multiples, the LCM is the first number that the lists have in common.

I can look for key division words for GCF, such as "split evenly" or "equal groups" and size words like "greatest" and "maximum." For LCM, I can look for key multiplication words like "repeatedly" and size words like "least" and "minimum."