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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
