The following are the divisibility rules for numbers from 2 through 10. It is helpful to know these rules because it saves time when doing calculations involving division.

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A NUMBER IS DIVISIBLE BY

2
If the last digit is even

3
If the sum of the digits is divisible by 3

4
If the last two digits form a number which is divisible by 4

5
If the last digit is a 5 or a 0

6
If the number is divisible by both 3 and 2

OR

If the unit digit (last digit) is even and the sum of the digits form a number divisible by 3

7

Take the last digit, double it, and subtract it from the rest of the number;
if the answer is divisible by 7 (including 0),

8
[b] If the last three digits form a number divisible by 8

9
If the sum of the digits is divisible by 9

10
If the number ends in 0

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See detailed examples of application of these laws here: http://samimath.com/math-tips-divisibility-rules/

nice tips

originalKsp:
The following are the divisibility rules for numbers from 2 through 10. It is helpful to know these rules because it saves time when doing calculations involving division.

****************************************
A NUMBER IS DIVISIBLE BY

2
If the last digit is even

3
If the sum of the digits is divisible by 3

4
If the last two digits form a number which is divisible by 4

5
If the last digit is a 5 or a 0

6
If the number is divisible by both 3 and 2

OR

If the unit digit (last digit) is even and the sum of the digits form a number divisible by 3

7

Take the last digit, double it, and subtract it from the rest of the number;
if the answer is divisible by 7 (including 0),

8
[b] If the last three digits form a number divisible by 8

9
If the sum of the digits is divisible by 9

10
If the number ends in 0

****************************************

See detailed examples of application of these laws here: http://samimath.com/math-tips-divisibility-rules/

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Check out this particular example on this topic, i found it veeeeeeeeeeeeeeeeeeery helpful . It actually shows the rule fo "11"

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http://9jababa.com/junior-mathematics-where-are-the-maths-gurus/
Check it out

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Thank for the explanation, that is my weak point in math