Curriculum › Math ›Grade 5

Grade 5 Math · Level 1, Place Value & Powers of 10

Greatest Common Factor & Least Common Multiple

How the lesson starts: Greatest Common Factor & Least Common Multiple

1. Camp Starlight

   Welcome to Camp Starlight! Counselor Max has 18 cupcakes and 24 cookies. He wants identical snack packs, with nothing left over, and as many packs as he can. Today we learn two camp superpowers: the GCF and the LCM!

2. Greatest common factor

   List the factors. 18: 1, 2, 3, 6, 9, 18. 24: 1, 2, 3, 4, 6, 8, 12, 24. They share 1, 2, 3 and 6. The greatest is 6, the greatest common factor. Max makes 6 packs, each with 3 cupcakes and 4 cookies!

3. Blinking lanterns

   Now the LCM. Two lanterns blink together. Blue blinks every 4 seconds, gold every 10. List multiples of 4: 4, 8, 12, 16, 20. Multiples of 10: 10, 20. They meet first at 20. That's the least common multiple!