Directions:

Notes: Divisibility rules are easy to learn and make factoring numbers easier.

A number is divisible by 3 when 3 divides that number evenly.

This also means that 3 is a factor of that number.

Examples:

A. 3 divides 12 evenly because 12÷3 = the whole number 4.

3 and 4 are both factors of 12.

B. 3 does not divide 13 evenly because 13÷3 = 4.33… not a whole number.

3 is not a factor of 13.

A short cut rule for 3.

A number is divisible by 3 if it’s digits add to a number that is evenly divided by 3.

Example: Is 132 divisible by 3? 1 + 3 + 2 = 6 and 6 is divisible by 3!

Answer: YES! 132 is divisible by 3 because 132÷3 = 43

Both 3 and 43 are factors of 132.

A shortcut rule for 9.

The same short cut works for 9. Add the digits.

If 9 divides the sum evenly then the number is divisible by 9.

Ex. 297 is divisible by 9 (2+9+7=18) Both 9 and 22 are factors of 198.

This workout has 10 questions.

You need to answer at least 90% of the questions correctly in 4 minutes or less.

Notes: Divisibility rules are easy to learn and make factoring numbers easier.

A number is divisible by 3 when 3 divides that number evenly.

This also means that 3 is a factor of that number.

Examples:

A. 3 divides 12 evenly because 12÷3 = the whole number 4.

3 and 4 are both factors of 12.

B. 3 does not divide 13 evenly because 13÷3 = 4.33… not a whole number.

3 is not a factor of 13.

A short cut rule for 3.

A number is divisible by 3 if it’s digits add to a number that is evenly divided by 3.

Example: Is 132 divisible by 3? 1 + 3 + 2 = 6 and 6 is divisible by 3!

Answer: YES! 132 is divisible by 3 because 132÷3 = 43

Both 3 and 43 are factors of 132.

A shortcut rule for 9.

The same short cut works for 9. Add the digits.

If 9 divides the sum evenly then the number is divisible by 9.

Ex. 297 is divisible by 9 (2+9+7=18) Both 9 and 22 are factors of 198.

This workout has 10 questions.

You need to answer at least 90% of the questions correctly in 4 minutes or less.