Divisibility Rules for 6th grade Math

What’s the point? These rules let you test if one number can be evenly divided by another, without having to do too much calculation!

When will you need to use the rules? Divisibility rules can be used: to find out if a number is prime or composite to help find factors of a number to find GCF and LCM when dealing with fractions

Divisibility rule for A number is divisible by 2, if the ones digit is divisible by 2 For example: 746 is divisible by 2… because 6 is divisible by 2 6÷2=3 (hint: any even # is divisible by 2!)

A number is divisible by 3, if the sum of the digits is divisible by 3 Divisibility rule for A number is divisible by 3, if the sum of the digits is divisible by 3 For example: 12,321 is divisible by 3 … because 1+2+3+2+1=9 9 is divisible by 3 9÷3=3

Divisibility rule for A number is divisible by 4, if the number formed by the last two digits is divisible by 4 For example: 824 is divisible by 4… because 24 is divisible by 4 24÷4=6

Divisibility rule for A number is divisible by 5, if the number ends in a 0 or 5 For example: 120 and 325 are both divisible by 5 120 ends in 0 325 ends in 5

Divisibility rule for A number is divisible by 6, if the number is divisible by 2 and 3 For example: 36 is divisible by 2 since 6 is even 36 is divisible by 3 since 3+6=9 and 9 is divisible by 3 So, 36 is divisible by 6!

Divisibility rule for A number is divisible by 7, if you can take the last digit, double it and subtract it from the remaining number and the answer is divisible by 7 For example: 203 is divisible by 7… because 3 doubled is 6, and 20-6=14 14 is divisible by 7 14÷7=2

Divisibility rule for A number is divisible by 8, if the last three digits are divisible by 8 For example: 1280 is divisible by 8… because 280 is divisible by 8 280÷8=34 so, 1280÷8=160

Divisibility rule for A number is divisible by 9, if the sum of the digits is divisible by 9 For example: 7056 is divisible by 9… because 7+0+5+6=18 and 18 is divisible by 9 18÷9=2

Divisibility rule for A number is divisible by 10, if the last digit is a zero For example: 100, 240, 3750, 48,720 are all divisible by 10

If you memorize the divisibility rules, math will become easier!

Let’s review… Write these in your notes! 2 if the ones digit is divisible by 2 3 if the sum of the digits is divisible by 3 4 if the # formed by the last two digits is divisible by 4 5 if the last digit is a 0 or 5 6 if the # is divisible by 2 and 3 9 if the sum of the digits is divisible by 9 10 if the last digit is a 0

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