The Divisibility Test

When given a number and asked to find out what all divides into that number can be challenging and even more challenging the higher the number you go. Last week on Monday we learn the Divisibility Tests for the numbers 2-12. We wouldn't use 1 because everything is divisible by 1.This method is way easier than writing all the division out by hand, which I have done many time until my hand would cramp up. Especially on a test when you forget your calculator and home and the other calculators are in use by other students and you are stuck writing them all by hand.

When our class got to the number 7, our Teacher told us that the rule is so complex that it is easier to do the division. Test 11 on Divisibility was the most confusing one for me to do. Divisibility by Eleven: Find the sum of the odd numbered digits (odd sum) and the sum of the even numbered digits (even sum). Take the difference between odd sum and even sum. If this difference is divisible by 11, the the original number is divisible by eleven. An example would be the number 7234952. So first take the odd digit numbers 7+3+9+2=21 and even digit numbers 2+4+5=11 and subtract the two numbers 21-11=10, Ten is not divisible by eleven so the rule would not apply here. Rules 2,3,4,5,6,8,9,10 and 12 can be found here.