Download least common multiple (LCM)

5-1
5-1 Least
LeastCommon
CommonMultiple
Multiple
Warm Up
Lesson Presentation
Course
Course
11
5-1 Least Common Multiple
Warm Up
Write the first five multiples of each
number.
1. 5
5, 10, 15, 20, 25
2. 6
6, 12, 18, 24, 30
3. 10
10, 20, 30, 40, 50
4. 12
12, 24, 36, 48, 60
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5-1 Least Common Multiple
Learn to find the least common multiple
(LCM) of a group of numbers.
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5-1 Least Common Multiple
Vocabulary
least common multiple (LCM)
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5-1 Least Common Multiple
Remember!
A multiple of a number is the
product of the number and any
nonzero whole number.
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5-1 Least Common Multiple
The smallest number that is a multiple of
two or more numbers is the least
common multiple (LCM). Unit 2
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5-1 Least Common Multiple
Remember!
The prime factorization of a number is
the number written as a product of its
prime factors.
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5-1 Least Common Multiple
Additional Example 2C: Using Multiples to Find
the LCM
Find the least common multiple (LCM).
Method 3: Use prime factorization.
6 and 20
6=2•3
20 = 2
•2•5
Write the prime factorization of
each number.
Line up the common factors.
2•3 •2•5
To find the LCM, multiply one
2 • 3 • 2 • 5 = 60 number from each column.
LCM: 60
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Use ladder to solve
5-1 Least Common Multiple
Additional Example 2D: Using Multiples to Find
the LCM
Find the least common multiple (LCM).
15, 6, and 4
15 = 3 • 5
6=3•
2
4=
22
Write the prime factorization of
each number in exponential form.
3 • 5 • 22
3 • 5 • 22 = 60
LCM: 60
Course 1
To find the LCM, multiply each
prime factor once with the
greatest exponent used in any of
the prime factorizations.
Use ladder method
5-1 Least Common Multiple
Check It Out: Example 2C
Find the least common multiple (LCM).
Method 3: Use prime factorization.
4 and 10
4=2•2
10 = 2
•5
Write the prime factorization of
each number.
Line up the common factors.
2•2 •5
2 • 2 • 5 = 20
LCM: 20
Course 1
To find the LCM, multiply one
number from each column.
Use ladder method
5-1 Least Common Multiple
Check It Out: Example 2D
Find the least common multiple (LCM).
12, 6, and 8
12 = 22 • 3
Write the prime factorization of
each number in exponential form.
6=2• 3
8 = 23
23 • 3
23 • 3 = 24
LCM: 24
Course 1
To find the LCM, multiply each
prime factor once with the
greatest exponent used in any of
the prime factorizations.
Use ladder method
5-1 Least Common Multiple
Lesson Quiz
Find the least common multiple (LCM).
1. 6, 14 42
2. 9, 12 36
3. 5, 6, 10 30
4. 12, 16, 24, 36 144
5. Two students in Mrs. Albring’s preschool class are
stacking blocks, one on top of the other. Reece’s
blocks are 4 cm high and Maddy’s blocks are 9 cm
high. How tall will their stacks be when they are
the same height for the first time?
36 cm
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