Answer:
196000 tiles.
Explanation:
The 28 m is 2800 cm. So a 28 x 28 meter square would be 2800 x 2800 centimeter square.
The tiles are 40 cm.
If you divide 40 from (2800 x 2800). (2800 x 2800) ÷40 = 196000
So 196000 tiles.
I'm not entirely sure if that's correct, but if it helps that's awesome.