Factor Tricks
How do you know if a number can be divided by 2?
If it is an even number? The last digit should be a 0, 2, 4, 6, or 8
What does GCF mean?
Greatest Common Factor
What do LCM mean?
Lowest Common Multiple or Least Common Multiple
How do you know if a number can be divided by 5?
The number should end in a 0 or 5.
What are the factors of 18?
1, 2, 3, 6, 9, 18
List the first 6 multiples of 4.
4, 8, 12, 16, 20, 24
How do you know if a number is divisible by 3?
Add the digits if the total is divisible by 3 so is the original number.
345: 3 + 4 + 5 = 12 so yes.
346: 3 + 4 + 6 = 13 so no.
What is the GCF of 6 and 15
6: 1, 2, 3, 6
15: 1, 3, 5, 15
GCF = 3
What is the LCM of 3 and 4?
3: 3, 6, 9, 12, 15
4: 4, 8, 12, 16
LCM: 12
How do you know if a number is divisible by 9?
Add the digits if the total is divisible by 9 so is the original number.
645: 6 + 4 + 5 = 15 so no.
774: 7 + 7 + 4 = 18 so yes.
12: 1, 2, 3, 4, 6, 12
28: 1, 2, 4, 7, 14, 28
GCF: 4
What is the LCM of 6 and 8?
6: 6, 12, 18, 24, 30
8: 8, 16, 24, 32
LCM: 24
How do you know if a number is divisible by 4?
If the last two digits are divisible by 4 then the original number is also divisible by 4.
3124: 24 is so yes.
500: 00 is so yes.
523: 23 is not so no.
What is the GCF of 18, 24, 36?
18: 1, 2, 3, 6, 9, 18
24: 1, 2, 3, 4, 6, 8, 12, 24
36: 1, 2, 3, 4, 6, 9, 12, 18, 36
GCF: 6
What is the LCM of 4, 9, 18?
4: 4, 8, 12, 16, 20, 24, 28, 32, 36
9: 9, 18, 27, 36, 45, 54
18: 18, 36, 54, 72
LCM: 36