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Divisibility Rules

Divisibility Rules. Introduction to Bits and Pieces III. The divisibility rules make math easier! Did you ever wonder how people could tell if something was divisible by a number just by looking at it? These rules are how they do it!

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Divisibility Rules

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  1. Divisibility Rules Introduction to Bits and Pieces III

  2. The divisibility rules make math easier! • Did you ever wonder how people could tell if something was divisible by a number just by looking at it? • These rules are how they do it! • Memorize a few simple rules and simplifying fractions and prime factorization will be so much easier. Divisibility Rules

  3. A number is divisible by 2 if • It is an even number, or • If the last digit of the number is even (0,2,4,6,8) • An example is 54,802. • What is another example? Come up with your own. Divisibility Rule for 2

  4. A number is divisible by 3 ifthe sum (answer to an addition problem) of the digits is divisible by 3. • An example is 642. • 6 + 4 + 2 = 12 and 12 is divisible by 3, therefore 642 is divisible by 3. • What is another example? Come up with your own. Divisibility Rule for 3

  5. A number is divisible by 4 if the last two digits of the number are divisible by 4. • An example is 948. • The last two digits of 948 are 48. 48 is divisible by 4, therefore 948 is divisible by 4. • What is another example? Come up with your own. Divisibility Rule for 4

  6. A number is divisible by 5 if the number ends in 0 or 5. • An example is 999,999,995 because the last digit is 5. • What is another example? Come up with your own. Divisibility Rule for 5

  7. A number is divisible by 6 if the number is divisible by both 2 and 3 (because 2 x 3 = 6). • An example is 72. 72 is even so it is divisible by 2. Also, the sum of the digits of 72 (7 + 2 = 9) is divisible by 3. Therefore, 72 is divisible by 6. • What is another example? Come up with your own. Divisibility Rule for 6

  8. A number is divisible by 8 ifthe last three digits are divisible by 8 (not as easy a rule). • An example is 35,120. 120 is divisible by 8, therefore, 35,120 is divisible by 8. • What is another example? Come up with your own. Divisibility Rule for 8

  9. A number is divisible by 9 if the sum of the digits is divisible by 9 (almost the same rule as 3). • An example is 45. 4+5 = 9, therefore 45 is divisible by 9. • Another example is 864. 8+6+4=18, therefore 864 is divisible by 9. • What is another example? Come up with your own. Divisibility Rule for 9

  10. A number is divisible by 10 if the last digit of the number is 0. • An example is 620. 620 ends in zero, therefore, 620 is divisible by 10. • What is another example? Come up with your own. Divisibility Rule for 10

  11. A number is divisible by 12 if the number is divisible by both 3 and 4 (because 3x4=12). • An example is 60. 6+0=6 which means 60 is divisible by 3. Also, 60 is divisible by 4. Therefore, 60 is divisible by 12. • What is another example? Come up with your own. Divisibility Rule for 12

  12. A number is divisible by 15 if the number is divisible by 3 and 5 (because 3x5=15). • An example is 135. 1+3+5= 9 which means 135 is divisible by 3. 135 ends in 5 so it is divisible by 5. Therefore, 135 is divisible by 15. • What is another example? Come up with your own. Divisibility Rule for 15

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