Warm Up

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Warm Up
Lesson Presentation
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Warm Up Write the first five multiples of each
number. 1. 5 2. 6 3. 10 4. 12
5, 10, 15, 20, 25
6, 12, 18, 24, 30
10, 20, 30, 40, 50
12, 24, 36, 48, 60
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Learn to find the least common multiple (LCM) of
a group of numbers.
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Vocabulary
least common multiple (LCM)
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The smallest number that is a multiple of two or
more numbers is the least common multiple (LCM).
Unit 2
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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
Write the prime factorization of each number.

20 2 2 5
Line up the common factors.
2 3 2 5
To find the LCM, multiply one number from each
column.
2 3 2 5 60
LCM 60
Use ladder to solve
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Additional Example 2D Using Multiples to Find
the LCM Find the least common multiple (LCM). 15,
6, and 4
15 3 5
Write the prime factorization of each number in
exponential form.
6 3 2
4 22
To find the LCM, multiply each prime factor once
with the greatest exponent used in any of the
prime factorizations.
3 5 22
3 5 22 60
LCM 60
Use ladder method
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Check It Out Example 2C Find the least common
multiple (LCM). Method 3 Use prime
factorization. 4 and 10
4 2 2
Write the prime factorization of each number.

10 2 5
Line up the common factors.
2 2 5
To find the LCM, multiply one number from each
column.
2 2 5 20
LCM 20
Use ladder method
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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
To find the LCM, multiply each prime factor once
with the greatest exponent used in any of the
prime factorizations.
23 3
23 3 24
LCM 24
Use ladder method
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Lesson Quiz
Find the least common multiple (LCM). 1. 6, 14
2. 9, 12 3. 5, 6, 10 4. 12, 16, 24, 36 5.
Two students in Mrs. Albrings preschool class
are stacking blocks, one on top of the other.
Reeces blocks are 4 cm high and Maddys blocks
are 9 cm high. How tall will their stacks be when
they are the same height for the first time?
42
36
30
144
36 cm