Examples
Example 1: Find the LCM of 4, 7 and 14.
Solution:
Prime factors of 4 = 2, 2
Prime factors of 7 = 7
Prime factors of 14 = 2, 7
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, 7, 14) = 28.
Example 2: Find the LCM of 3, 6 and 9.
Solution:
Prime factors of 3 = 3
Prime factors of 6 = 2, 3
Prime factors of 9 = 3, 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(3, 6, 9) = 18.
Example 3: Find the LCM of 6, 7 and 21.
Solution:
Prime factors of 6 = 2, 3
Prime factors of 7 = 7
Prime factors of 21 = 3, 7
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, 7, 21) = 42.
Exercise
1. LCM(12,15,20) = 60
2. LCM(18,24,36) = 72
3. LCM(30,40,45) = 360
4. LCM(10,18,20) = 180
5. LCM(10,12,15) = 60
6. LCM(8, 4, 6) = 24
7. LCM(3,7,14) = 42
8. LCM(15, 25, 35) = 525
9. LCM(10,18,20) = 180
10. LCM(5,9,18) = 90