Question

How can we know that two digits whole number divisible by 3?

Answer 1

If the sum of digits of no. divisible by 3.

Then it will be divisible by 3.

ex.  27

  = 2 +7 = 9 which is divisible by 3.

Answer 2

there is a simple trick for this. add all face values of digits. if it is still a big number, keep on adding till you can recognise the number if it is a multiple of three. for example:-
123456789 . we will add it. we will get 45, which is a multiple of three. if you can still not recognise it, add 4+5. you will get 9, which is obviously a multiple of 3

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