Divisibility Rule for 3


 
 
Concept Explanation
 

Divisibility Rule for 3

Divisibility Rule for 3: This rule is used to check whether a number is divisible by 3 or not without performing long division. A number is divisible by 3, if the sum of its digits is divisible by 3. Otherwise the number is not divisible by 3. The remainder obtained by dividing the number by 3 is same as the remainder obtained by dividing the sum of its digits by 3.

ILLUSTRATION: Consider the number n = 7856421 .

The sum of the digits of n is 7 + 8 + 5 + 6 +4 +2 +1 = 33, which is divisible by 3. So, n is divisible by 3.

Let us now consider another number m = 78215.

The sum of its digits is 7 + 8 + 2 + 1 + 5 = 23, which is not divisble by 3. So, m is not divisble by 3.

This can also be verified by the actual division of 78215 by 3. The remainder obtained by dividing m by 3 is equal the remainder when 23 is divided by 3.Clearly , it is 2.

 
 


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