Barnal wrote:

I think this is a high-quality question and the explanation isn't clear enough, please elaborate. Mhhh, what is wrong with this :

10^n - 1 can be 9, 99, 999, 9999 so it seems to me that if q is not divisible by q then we can assure that it is not divisible by q.

Any help to explain where I am wrong ?

thanks

I would like to repeat Barnel's question .. 10 ^n - 1 should be 9, 99 (as n > 0 ) etcc which should be a multiple of 9 .. and as per the second option it is given that the Q is not divisible by 9

Then if Q is not divisible by 9 then the number in question (10 ^n - 1) should also be indivisible by Q right ?

please help me understand where Am i going wrong ..