Examples
Example 1: Find the LCM of 20, 30 and 40.
Solution:
Prime factors of 20 = 2, 2, 5
Prime factors of 30 = 2, 3, 5
Prime factors of 40 = 2, 2, 2, 5
Write these prime factors into the venn diagram for each number.
Multiply each prime factor in the venn diagram to find the LCM.
Therefore, LCM(20, 30, 40) = 120.
Example 2: Find the LCM of 4, 6 and 12.
Solution:
Prime factors of 4 = 2, 2
Prime factors of 6 = 2, 3
Prime factors of 12 = 2, 2, 3
Write these prime factors into the venn diagram for each number.
Multiply each prime factor in the venn diagram to find the LCM.
Therefore, LCM(4, 6, 12) = 12.
Example 3: Find the LCM of 6, 12 and 15.
Solution:
Prime factors of 6 = 2, 3
Prime factors of 12 = 2, 2, 3
Prime factors of 15 = 3, 5
Write these prime factors into the venn diagram for each number.
Multiply each prime factor in the venn diagram to find the LCM.
Therefore, LCM(6, 12, 15) = 60.
Exercise
1. LCM(18,24,36) = 72
2. LCM(30,45,60) = 180
3. LCM(8,10,28) = 280
4. LCM(5,9,18) = 90
5. LCM(8,12,30) = 120
6. LCM(2,3,9) = 18
7. LCM(6,7,21) = 42
8. LCM(10,12,15) = 60
9. LCM(15, 25, 35) = 525
10. LCM(7,21,35) = 105