Amazing Math magic.

Question

Amazing Math magic.

faiqraees · Answer

Here I am going to demonstrate you a really cool math trick that is just awesome. It deals with the magnificent significance of 9 and the symmetry of reversed numbers that revolves around it.
Since I have revealed the main idea, many people will guess the trick, for people interested, I will tell the technique at the end.
The trick is you're gonna take a number of digits N. Reverse the number and subtract from it. Now you will give me any N-1 digits and I can tell you the the remaining digit with pinpoint accuracy.
For example, you take $$\large\rm \ 653 $$ Now reverse it and subtract from it. $$\large\rm \ 653-356 = 297 $$ Provide me any two digit and I will tell you the remaining digit. Suppose you say 2 and 7. I will tell you that 9 is the remaining digit.

kainui · Answer

Ok I picked a 4 digit number so I now give you 3 digits right? Here they are:

0, 0, 0

faiqraees · Answer

9

faiqraees · Answer

@Kainui so? was it correct?

kainui · Answer

Yeah! I picked 9879, so 9879 - 9789 = 0090.

faiqraees · Answer

Yeah the trick NEVER fails.

hartnn · Answer

if I give you 1 and 8, 
will you tell 9 or 0 ?
because both will be correct, right?

faiqraees · Answer

yes @hartnn

faiqraees · Answer

But there is more probability that it will be 9

faiqraees · Answer

@hartnn I actually did some tests and it seems that 0 cannot be the remaining digit unless all digits are same which isn't covered by the riddle. But I could be wrong here

hartnn · Answer

so 108 cannot be the difference of any 3 digit number and its reverse?

faiqraees · Answer

yeah because For 8 to come as a difference it can only happen if the last digit of the first number is 9 and the last digit of second number is 1. Which means the first digit of the first number has to be 1 and the first digit of second number has to be 9. Which will give us a negative answer.