Students will learn how to find the GCD of whole numbers by listing factors, and the LCM by listing multiples.
Highest Common Factor and Lowest Common Multiple Part 1 by MathsMasterOrg
Do these Khan Academy exercises, in any order:
Conclude by leading this investigation:
Subtraction Magic with 3 Digits
by MathPickle
6.NS.B.4: Find the greatest common factor of two whole numbers less than or equal to 100 and the least common multiple of two whole numbers less than or equal to 12. Use the distributive property to express a sum of two whole numbers 1-100 with a common factor as a multiple of a sum of two whole numbers with no common factor. For example, express 36 + 8 as 4 (9 + 2).