Download Lesson 6

LESSON 6
FACTORS AND DIVISIBILITY
FACTORS:
• The FACTORS of a number are the whole
numbers that can divide the number without a
remainder.
EXAMPLES
• The factors of 12 are 1, 2, 3, 4, 6, 12.
• The factors of 20 are 1, 2, 4, 5, 10, 20.
• The factors of 21 are 1, 3, 7, 21.
GCF
• The Greatest Common Factor is the largest factor two numbers
have in common.
• Lets look at 51 and 12.
• The factors of 51 are 1, 3, 17, 51.
• The factors of 12 are 1, 2, 3, 4, 6, 12.
• 3 is the biggest number that is in BOTH lists. So 3 is the GCF for
51 and 12.
EXAMPLE
• What is the GCF of 18 and 30?
• Factors of 18: 1,2,3,6,9,18.
• Factors of 30: 1,2,3,5,6,10,15,30.
• Factors in both lists: 1,2,3,6
• 6 = GCF
DIVISIBILITY
• The capability of a whole number to be divided by
another whole number with no remainder is called
divisibility.
DIVISIBILITY TESTS (2-4)
• There are some quick ways to check if a number is divisible by another number.
• Is a number divisible by 2?
• If the last digit is even
• Is a number divisible by 3?
• If the sum of the digits can be divided by 3
• Is a number divisible by 4?
• If the last two digits can be divided by 4
DIVISIBILITY TEST (5, 6)
• Is a number divisible by 5?
• The last digit is 0 or 5
• Is a number divisible by 6?
• The number can be divided by 2 and 3
DIVISIBILITY TEST (8-10)
• Is a number divisible by 8?
• If the last 3 digits can be divided by 8
• Is a number divisible by 9?
• If the sum of the digits is divisible by 9
• Is a number divisible by 10?
• If the last digit in the number is 0