Divisibility by 3 Workout

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.