Saturday, October 3, 2009

 find out if a number is divisible by seven(7):

Take the last digit, double it, and subtract it from the rest of the 

number. 

If the answer is more than a 2 digit number perform the above 

again. 

If the result is 0 or is divisible by 7 the original number is also 

divisible by 7. 





Example 1 )   259 

9*2= 18. 

25-18 = 7 which is divisible by 7 so 259 is also divisible by 7. 





Example 2 ) 2793 

3*2= 6 

279-6= 273 



now 3*2=6 

27-6= 21 which is divisible by 7 so 2793 is also divisible by 7 . 





Now find out if  following are divisible by 7 



1) 2841 

2) 3873 

3) 1393 

4) 2877

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