1. Wednesday, October 13 (Blue) Thursday, October 14 (Gold)
Fill in planner (Practice 5-1)
Bell Work (Write the prime factorization of each number)

2. Objective
SWBAT find the Least Common Multiple (LCM) and compare and order fractions.

3. Vocabulary Multiple least common multiple (LCM)
least common denominator (LCD)

4. A multiple of a number is the product of the number and any nonzero whole number.

5. least common multiple (LCM): The smallest number that is a multiple of two or more numbers.
least common denominator (LCD): The smallest number that is the multiple of two or more denominators.

6. Today, the school’s baseball and soccer teams had games
Today, the school’s baseball and soccer teams had games. The baseball team plays every 7 days. The soccer team plays every 3 days. When will the teams have games on the same day again?
3,7
7: 7, 14, 21 , 28, 35, 42,
List multiples of 3 and 7.
Find the smallest number that is in all the lists.
3: 3, 6, 9, 12, 15, 18, 21, . . .
LCM: 21. In 21 days, both teams will have game on the same day again.

7. The prime factorization of a number is the number written as a product of its prime factors.
Remember!

8. Example 2: Find the LCM of 16 and 36
16 = 24
Write the prime factorizations
36 = 22• 32
Use the greatest power of each factor.
24 • 32
Multiply.
16 • 9 = 144
LCM: 144

9. Example 3: Find the LCM of 5a4 and 15a
Write the prime factorizations
15a = 3• 5 •a
Use the greatest power of each factor.
3 • 5• a4
Multiply.
15a4
LCM: 15a4

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13. 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 =
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

14. Find the least common multiple (LCM). Method 1: Use a number line.
Check It Out: Example 2A
Find the least common multiple (LCM).
Method 1: Use a number line.
2 and 3
Use a number line to skip count by 2 and 3.
The least common multiple (LCM) of 2 and 3 is 6.

15. Find the least common multiple (LCM). Method 2: Use a list.
Check It Out: Example 2B
Find the least common multiple (LCM).
Method 2: Use a list.
3, 4, and 9
3: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, . . .
List multiples of 3, 4, and 9.
4: 4, 8, 12, 16, 20, 24, 28, 32, 36, …
Find the smallest number that is in all the lists.
9: 9, 18, 27, 36, 45, . . .
The least common multiple of 3, 4, and 9 is 36.

16. Find the least common multiple (LCM).
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 = • 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

17. Find the least common multiple (LCM).
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

18. Lesson Quiz
Find the least common multiple (LCM).
1. 6, , 12
3. 5, 6, , 16, 24, 36
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? 42 36 30
144
36 cm