Prime, composite, square?
Which of the following numbers is prime?
18, 19, 20, or 21
19
Is the following number divisible by 2? What is the rule of divisibility for 2?
456
yes, 456/2 = 228
The rule of divisibility for 2 is that all even numbers are divisible by 2.
Find the GCF by listing all of the factors of 14 and 35.
Factors of 14: 1 x 14, 2 x 7
Factors of 35: 1 x 35, 5 x 7
GCF = 7
Find the LCM by Listing the Multiples of 4 and 7
4, 8, 12, 16, 20, 24, 28, 32, 36...
7, 14, 21, 28, 35...
LCM = 28
Find the GCF of 48 and 72 using upside down division.
2 48 72
2 24 36
2 12 18
3 6 9
2 3
GCF = 2x2x2x3 = 24
Is this number prime or composite? Why?
22
composite, has multiple factor pairs
1x22
2x11
Is the following number divisible by 5? What is the divisibility rule for 5?
245
yes, 245/5 = 49
To be divisible by 5, the number must end in either 0 or 5.
Find the GCF of 48 and 56 by listing the factor pairs.
48: 1x48, 2x24, 3x16, 4x12, 6x8
56: 1x56, 2x28, 4x14, 7x8
GCF: 8
Find the LCM by listing the multiples of 6 and 8
6, 12, 18, 24, 30, 36...
8, 16, 24, 32, 40...
LCM = 24
Find the LCM of 30 and 18 using upside down division.
2 30 18
3 15 9
5 3
LCM: 2x3x5x3 = 90
Which of these numbers is a perfect square? why?
36, 5, 10, or 20
36, it makes a 6x6 square
Is the following number divisible by 3? What is the rule for 3?
51
yes, 51/3 = 17
Rule for dividing by 3: If the sum of the digits adds to 6 then it is divisible by 3.
5+1 = 6
True or false: The GCF of 25 and 50 is 50?
False, the GCF of 25 and 50 is 25.
Find the LCM by Listing the Multiples of 4, 6, and 9
4, 8, 12, 16, 20, 24, 28, 32, 36, 40...
6, 12, 18, 24, 30, 36, 42...
9, 18, 27, 36, 45, 54...
LCM = 36
Find the GCF 65 and 104 using upside down division.
13 65 104
5 8
GCF: 13
Which of the following numbers is not composite?
47, 48, 49, 50
47
Use the distributive property to rewrite the expression.
3(2+5)
Distribute: multiply 3x2 and 3x5
New expression: 6+15
Find the GCF by listing the factors of 20, 35, and 45
20: 1x20, 2x10, 4x5
35: 1x35, 5x7
45: 1x45, 3x15, 5x9
GCF = 5
Find the LCM by listing the Multiples of 3 and 8
3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42, 45, 48, 51
8, 16, 24, 32, 40, 48, 56, 64
LCM = 48
Find the GCF and LCM of 8 and 12 using upside down division.
4 8 12
2 3
GCF: 4
LCM: 4x2x3 = 24
What is the only even prime number?
2
Is the following number divisible by 1? 2? 3? 4? 5? 6? 7? 8? 9? 10?
4860
What is 1, 2, 3, 4, 5, 6, 9, 10
Find the GCF by listing the factors of 42 and 84
42: 1x42, 2x21, 3x14, 6x7
84: 1x84, 2x42, 3x28, 4x21, 6x14, 7x12
What is GCF = 42
Find the LCM by Listing the Multiples of 7 and 12
7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84
12, 24, 36, 48, 60, 72, 84
LCM = 84
Find the GCF and LCM of 125 and 50 using upside down division.
25 125 50
5 2
GCF: 25
LCM: 25x5x2 = 250