How Can You Tell?

How can you just tell if a number goes into another number evenly with out dividing? With these simple rules.


Divisibility by two: If the last digit, is even, the original number is divisible by two.


This number works: 2012 (two is even), this number does not work: 2011 (one is odd)


Divisibility by three: If the sum of the digits is divisible by 3, then the original number is divisible by 3.


This number works: 2136 (2+1+3+6=12, 3 goes into 12 evenly) This number does not: 2137 (2+1+3+7=13, 3 does not go into 13 evenly)


Divisibility by four: if the last two digits form a number that is divisible by four, then the original number is divisible by four.


This number works: 2136 (4 goes into 36 with no remainder) This number does not: 2134 (4 does not go into 34 evenly)


Divisibility by five: If the last digit is either 0 or 5, then the original number is divisible by 5.


This number works: 2155, This number does not: 2151


Divisibility by six: if the number is divisible by 2 AND 3, then it is divisible by 6.


This number works: 2136 (follows rules of divisibility by 2 AND 3) This number does not: 3242


Divisibility by seven: don't, just get out the calculator or a pencil and paper.


Divisibility by eight: If the last three digits form a number that is divisible by eight, then the original number is divisible by eight.


This number works: 133,760 (8 goes evenly into 760) This number does not: 133,766


Divisibility by nine: If the sum of the digits is divisible by 9, then the original number is divisible by 9. 


This number works: 3,465 (3+4+6+5=18, 9 goes evenly into 18) This number does not: 3,565


Divisibility by ten: If the last digit is 0, then the original number is divisible by ten.


This number works: 5730 This number does not: 2343


Divisibility by twelve: If the number is divisible by 3 AND 4, then it is divisible by 12. 


This number works: 24 (both 3 and 4 go into 24 evenly) This number does not: 30 (even though it is divisible by 3 it is not divisible by 4, therefore it is not divisible by 12)


Those are the basics of division, you'll never need a calculator again! :)