SOLUTION: A tiled floor of a room has a dimension m*m sq-m dimensions of tile used are n*n sq-m. All tiles used are green tiles except diagonal tiles are red. After some years some green til

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Question 890619: A tiled floor of a room has a dimension m*m sq-m dimensions of tile used are n*n sq-m. All tiles used are green tiles except diagonal tiles are red. After some years some green tiles are replaced by red tiles to form alternate red and green tiles pattern how many green tiles are removed? (m not equal to n)
Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
If the floor is completely covered with the tiles, then m%2Fn is a positive integer.
That is the number of tiles along each side of the square room,
and it is also the number of tiles in the diagonal.
The total number of tiles is %28m%2Fn%29%5E2 .

If m%2Fn is even, in an alternating pattern, half of the tiles would be red.
The final number of red tiles would be
%28m%2Fn%29%5E2%2F2
The number of green tiles replaced (the number of red tiles added) would be
%28m%2Fn%29%5E2%2F2-m%2Fn=%28m%2Fn%29%28m%2F2n-1%29

If m%2Fn is an odd number, an alternating pattern with a red diagonal would have
%28%28m%2Fn%29%5E2%2B1%29%2F2 red tiles and %28%28m%2Fn%29%5E2%2B1%29%2F2 green tiles.
The number of green tiles to be replaced (the number of red tiles to be added) would be


UNFORTUNATELY, there is no simple formula that covers both cases (when m%2Fn is even, and when m%2Fn is odd).
If you want a single formula, I would have to write something complicated, like
m%5E2%2F2n%5E2-m%2Fn-%281%2F4%29%28-1%2B%28-1%29%5E%28m%2Fn%29%29 or %281%2F2%29%28m%2Fn-1%29%5E2-%281%2F4%29%281%2B%28-1%29%5E%28m%2Fn%29%29

For m%2Fn=9 , which is odd, we are replacing
%281%2F2%29%28%28m%2Fn%29-1%29%5E2=%281%2F2%29%289-1%29%5E2=%281%2F2%29%2A8%5E2=64%2F2=32 tiles, or
tiles, or
tiles.
The new (replacement) red tiles are the ones in the green triangles.
There are 7%2B5%2B3%2B1=16 in each triangle.