Chapter 5 Number
Patterns and
Fractions
5.4 - Least Common Multiple
Pages- 250-253
Title: Jan 30-8:49 AM (1 of 5)
NOTES:(5.4) Least Common Multiple
(LCM)
The LCM of two or more numbers is the smallest
multiple those numbers share
* Key idea p. 251 *
3 ways to find LCM:
1) List- all multiples; find the smallest multiple each of
the numbers "share."
2) Prime factorization - find prime factorization of all
numbers; use each prime factor the greatest number of
times it is a factor of any one of the numbers
3) Table- find all factors until no more shared factors
exist; multiply left column times bottom row
Title: Jan 24-10:48 PM (2 of 5)
Guided Practice
Do # 8 & 10 like this (multiple answers)
5) 6 : 6, 12, 18, 24, 30, 36...
8 : 8, 16, 24
24 1 = 24
24 2 = 48
24 3 = 72
24 4 = 96
24, 48, 72, 96
9) 20: 20, 40, 60, 80...
30: 30, 60, 90
1 x 60 = 60
2 x 60 = 120 (too big)
60
Title: Jan 24-10:54 PM (3 of 5)
Do #16 & 18 like this (List)
17) 2: 2, 4, 6, 8, 10, 12, 14, 16, 18,
20, 22, 24, 26, 28, 30...
3: 3, 6, 9, 12, 15, 18, 21, 24, 27,
30...
5: 5, 10, 15, 20, 25, 30...
LCM (2 , 3 , 5 = 30)
Do #20 & 22 like this (factor trees)
21)
22
36
2 x 11
6x6
2x3x2x3
2 x 2 x 3 x 3 x 11 =
36 x 11
LCM 22, 36 = 396
Title: Jan 24-11:03 PM (4 of 5)
36
x 11
36
360
396
Do # 24 & 26 like this (table)
23)
27
9 3
45
5
9 x 3 x 5 = 9 x 15
LCM (27, 45) = 135
notice: you may divide using
smaller #'s and you'll still get
the same answer
27
3 9
3 3
45
15
5
3 x 3 x 3 x 5 = 9 x 15 = 135
#40 = 2 pts
Title: Jan 24-11:13 PM (5 of 5)
15
x 9
135