Notes 9/9/10 Prime Time Definitions

Greatest Common Factor (GCF): The greatest factor that two (or more!) numbers share. Ex: The GCF for 36 and 24 is 12.Least Common Multiple (LCM): The smallest number that is a multiple of two numbers. Ex: 12 is the LCM of 3 and 4.

Greatest Common Factor

1) Find the Prime Factorization 2) Put the results in a Venn Diagram3) The shared numbers go in the

shared space (middle) of the Venn Diagram

4) Multiply the shared number together = GCF

Factors of 56

What is the GCF for these two numbers? _______

Factors of 56

Factors of 28

The numb

ers that are the

same

Leftover

numbers

Leftover

numbers

Factors of 28

Factors of 56

What is the GCF for these two numbers? _______

Factors of 56

Factors of 28

GCF Practice

• Find the GCF for the following numbers (use a Venn Diagram)- 24 and 30

– 15 and 60

– 30 and 50

Least Common Multiple

• 1) Find the GCF• 2) Place the leftover numbers (ones

not shared) in the Venn Diagram.• 3) Multiply all numbers in the Venn

Diagram = LCM

LCM Practice

Leftover numbers go here

20 50

Leftover numbers go here

GCF

What is the LCM for these two numbers? _______

LCM Practice

• Find the LCM of these two numbers:

• 5 and 7

• 10 and 15

REAL LIFE PROBLEM SOLVING USING GCF AND

LCM• You have 27 Reese’s Cups and

66 M & M’s.

Including yourself, what is the greatest number of friends you can enjoy your candy with so that everyone gets the same amount?

REAL LIFE PROBLEM SOLVING USING GCF AND

LCMMolly’s uncle donated 100 cans of juice and

20 packs of cheese crackers for the school picnic. Each student is to receive the same

number of cans of juice and the same number of packs of crackers.

• What is the largest number of students that can come to the picnic and share the food equally?

• How many cans of juice and how many packs of crackers will each student receive?

REAL LIFE PROBLEM SOLVING USING GCF AND LCM

Mrs. McCrary and 23 of her students are planning to eat hot dogs at the upcoming

DMS picnic. Hot dogs come in packages of 12 and buns come in packages of 8.

• What is the smallest number of packs of dogs and the smallest number of packs of buns Mrs. McCrary can buy so that everyone INCLUDING HER can have the same number of hot dogs and there are no leftovers?

• How many dogs and buns does each person get?