Divisibility Tests by Composite Numbers like 6, 12, 14, 15, 18 and so on

First you need to understand what is a COMPOSITE NUMBER then we will learn the rules to check the divisibility of them. A Composite Number is one which is NOT a PRIME NUMBER. It has factors other than the 1. For Ex. factors of 6 are 2 and 3 and similarly factors of 12 are 3 and 4.

(1) Is the 204 is divisible by 6 ?
  • Just split the number 6 into two factors like 2 and 3.  
  • And check whether 204 is divisible by these two numbers separately or not?
  • 204 is perfectly divisible by 2 as it is an even number.
  • 204, digits total 2+4 = 6 which is a multiple of 3 that means it is also divisible by 3.
  • So it is perfectly divisible 6.
Just remember all these steps will be done in your brain. So it will take seconds to you to guess whether the given number is divisible by the given composite number or not.

(2) Is the 1068 is divisible by 12 ?
  • Splitting the number 12 into 3 and 4. 
  • 1068 is divisible by 3 as 1+0+6+8 = 15, a multiple of 3
  • And it is also divisible by 4 as 68 is divisible by 4.
  • So, 1068 is perfectly divisible by 12
(3) Is the 938 is divisible by 14 ?
  • Factors of 14 are 2 and 7.
  • 938 is an even number so it is completely divisible by 2.
  • and 938 is also perfectly divisible by 7.
  • So, 938 is divisible by 14 .
(4) Is the 345 is divisible by 15 ?
  • Factors of 15 are 3 and 5.
  • 345 is divisible by 3 as 3+4+5 = 12 (a multiple of 3).
  • It is also divisible 5 since the unit's digit is 5.
  • So, 345 is perfectly divisible by 15.
(5) Is the 1134 is divisible by 18 ?
  • Factors of 18 are 9 and 2.
  • 1+1+3+4 = 9 therefore 1134 is divisible by 9.
  • 1134 is an even number so it is also divisible by 2.
  • So, 1134 is divisible by 18.

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