Tuesday, July 9, 2019

Test of Divisibility



Divisibility by 2 



Any number whose last digit is either even number or zero is divisible by 2.


Example: 


  • Consider the number 668

  •  last digit is  8 which is even

  • so 668 is divisible by 2



Divisibility by 3



A number is divisible by 3  if the sum of its digits is divisible by 3 


Example: 


  • Consider the number 432

  • 4+3+2=9

  • 9 is divisible by 3

  • so 432 is divisible by 3






Divisibility by 4


If the last two digits of a number are divisible by 4, then that number is  divisible by 4.


Example: 








  • consider the number 6424. 



  • the last two digits i.e.24. 



  • 24 is divisible by 4, 



  • so 6424  is  divisible by 4.









Divisibility by 5 



Numbers with last digit 0 or 5 are always divisible by 5.

Example: 645,565,895,650,760 etc.


Divisibility by 6 



Numbers which are divisible by both 2 and 3 are divisible by 6.


Example: ,


  • consider the number 540 



  • since the last digit is 0 , the number is divisible by 2



  • sum of digits 5+4+0=9,  9 is divisible by 3, so 540 is divisible by 3

  • since 540 is divisible by both 2 and 3, 540 is divisible by 9



Divisibility by 8 



If the last three digits of a number are divisible by 8, then the number is  divisible by 8.


Example:




  • Take number 9240. 

  • Consider the last two digits i.e.  240.

  •  As 240 is divisible by 8,

  •  the original number 9240 is also divisible by 8.




Divisibility by 9



 if the sum of digits of the number is divisible by 9, then the number itself is divisible by 9.


Example:




  •  Consider 6543, 

  •  the sum of its digits (6+5+4+3) is 18, which is  divisible by 9, 

  •  so 6543 is  divisible by 9




Divisibility by 10 



 any number whose last digit is 0, is divisible by 10.


Example: 680,230,3000 etc.


Divisibility by 11



If the difference of the sum of alternative digits of a number is zero or divisible by 11 then that number is divisible by 11 


consider the number 66429




  • Group the alternative digits i.e. digits which are in odd places together and digits in even places together. Here 6,4,9 and  6,2 are two groups.

  • Take the sum of the digits of each group i.e. 6+4+9=19 and 6+2=8

  • Now find the difference of the sums; 19-8= 11

  • the difference 11 is divisible by 11

  • Therefore, 66429 divisible by 11.




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