My favorite thing about math is when there are tricks and short cuts to help you get to the answer faster than the original way. Today we learned a few rules that will help you quickly come to the conclusion if it is divisible by that number or not. So here it is:
Divisibility by two: if the last digit is even, the original number will be divisible by two.
Divisibility by three: if the sum of the digits is divisible by 3, then the original number is divisible by three.
Divisibility by four: If last 2 digits form a number that is divisible by four, then the original number is divisible by four.
Divisibility by five: If the last digit is either 0 or 5, then the original number is divisible by 5.
Divisibility by six: If the number is divisible by 2 and 3, then it is divisible by six.
Divisibility by eight: If the last three digits form a number that is divisible by eight, then is divisible by 8.
Divisibility by nine: if the sum of the digits is divisible by 9, then the original number is divisible by 9.
Divisibility by ten: if the last digit is 0, then the original number is divisible by ten.
Divisibility by twelve: if the number is divisible by 3 and 4, then the it is divisible by 12.
Unfortunately, there are no rules for seven or eleven that are in my opinion short cuts. I would now like to go through a few examples:
example number #1: 2,126 is divisible by 2 because six is divisible by 2, 4 because six plus two is eight which is divisible by four so that makes 2126 is divisible by 4. 6 because this number is divisible by two and three.
example number #2: 2000 is divisible by 2, 4, 5,8, and 10.
My Math Blog 