Least Common Multiple

1. Agenda Friday,
Dec. 4
Homework 13 p. 239 # 1 - 13
Correct homework
Least Common Multiple

2. p. 234 
Find GCF 
9.  3, 15 = 3 
10. 16, 20 = 4
11. 12, 36 = 12
12. 11, 30 = 1
Simplify
22. 10/12 = 5/6
23. 8/20 = 2/5
24. ­ 2/16 = ­2
25. 25/100 = 1/4
26. ­ 120/125 = ­ 24/25
27. 15/45 = 1/3
28. ­20/­75 = 4/15
29. 16/124 = 4/31
30. ­ 18/81 ­ ­ 2/9
31. ­ 10/65 = ­ 2/13
32. ­14/84 = 1/6

3. What is the least common
multiple?
The least common multiple of two numbers is the smallest number (not
including 0 or 1) that is a multiple of both.
Example: What is the LCM of 3 and 4?
Multiples of 3: 3, 6, 9, 12, 15, 18...
Multiples of 4: 4, 8, 12, 16, 20...
The least common multiple of 3 and 4 is 12.

4. Multiples of 10:
Multiples of 30:
The LCM of 10 and 30 is:
Multiples of 8:
Multiples of 24:
The LCM of 8 and 24 is:
Find the LCM of the following
number pairs.

5. You can also find the LCM using
prime factorization.
2 12 2 8Write the prime factorization
2 6 2 4
3 2
Use the GREATEST power of
2
2
* 3 2
3
each factor.
2
3
* 3
8 * 3 = 24 Write the Least Common Multiple
as a product.

6. Use a venn diagram.
12
15
3 * 5
2 * 2 * 3
5
23
2
2 * 2 *
3 * 5
2
2
* 3
* 5
4 * 3 *
5 = 60
Use the venn diagram just like for GCF. But
multiply all the prime factors for the LCM

7. Find the LCM of the following
expressions using the
venn diagram method.
36 and 12 20 and 6

9. We can also use a "double ladder" method.

10. Find the LCM of the following
number pairs using the
ladder method.
8 and 15 15 and 30

11. Find the LCM of the following
number pairs using the
ladder method.
32 and 12 24 and 10

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