GCF and LCM

GCF and LCM

Review and Reteach

When to use GCF

• to divide things into smaller sections

• to equally distribute sets of items

• to arrange something into rows or groups

• when you see - greatest number of, how many, share, no leftovers

  
  
  
  
  

List the factors of 24 and 36

24-1,2,3,4,6,8,12,24
36-1,2,3,4,9,12,18,36
Greatest Factor in Common = 12

List factors of 18 and 27

18-1,2,3,6,9,18
27-1,3,9,27
Largest factor in common = 9

List factors of 24, 48, 84

24-1,2,3,4,6,8,12,24
48-1,2,3,4,6,8,12,16,24,48
84-1,2,3,4,6,7,12,14,21,28,42,48
GCF = 12

Factors of 16 and 20

16-1,2,4,8,16
20-1,2,4,5,10,20
Greatest Common Factor - 4

Factors of 32, 24, and 16

32-1,2,4,8,16,32
24-1,2,3,4,6,8,12,24
16-1,2,4,8,16
GCF = 8

Factors of 63 and 42

63-1,3,7,9,21,63
42-1,2,3,6,7,14,21,42

GCF = 21

When to use LCM

• when an event will be repeating over and over

• to figure out when something will happen again at the same time

• when you see - least number of, happen at the same time, smallest number, cycle, repetition

Multiples of 3 and 5

3-3,6,9,12,15
5-5,10,15
Smallest multiple in common = 15

Multiples of 6 and 16

6-6,12,18,24,30,36,42,48
16-16,32,48

Multiples of 3, 6, and 9

3-3,6,9,12,15,18
6-6,12,18
9-9,18
LCM=18

Multiples of 6 and 8

6-6,12,18,24
8-8,16,24
LCM=24
6 x ? = 24  4
8 x ? = 24   3

Multiples of 3 and 7

3-3,6,9,12,15,18,21
7-7,14,21
LCM=21

Multiples of 40 and 60

40-40, 80,120
60-60,120
LCM=120