Divisibility Rules

Monday's lesson will be about using divisibility rules to test for division by 2, 3, 5, 6, 9, 10. A whole number is divisible by another whole number if the remainder in the division is zero. The result (quotient) must be a whole number.

Below are the divisibilty rules students will be learning. While students are not required to memorize them at this point, recall of these handy shortcuts will benefit them in the future.

• All even numbers are divisible by 2.
• A number is divisible by 3 if the sum of the digits is divisible by 3. (Sum of digits is the answer when adding the digits together. For example, 123 is divisible by three because 1+2+3 = 6, and six is divisible by three.)
• A number is divisible by 6 if it is divisible by BOTH 2 and 3.
• A number is divisible by 9 if the sum of it's digits is divisible by 9. (378 is divisible by 9 because 3+7+8=18, and 18 is divisible by 9.)
• A number is divisible by 10 if it ends in 0.
• A number is divisible by 5 if it ends in 0 or 5.