The answer will depends on the size of the bag, how much cement it makes and the thickness of the cement layer. Since you have not bothered to share these crucial bits of information, I cannot provide a more useful answer.
the size of you!>!CK
Depends on the size of cement bricks.
depends how deep
20
One square metre is the area of a square whose sides measure exactly one metre.
the size of you!>!CK
4
about 10square meters
Depends on the size of cement bricks.
depends how deep
2500 tiles
20
One square metre is the area of a square whose sides measure exactly one metre.
83m^2
6
That depends on how thin you spread it. If it's a meter thick, it only covers one square meter. If it's a centimeter thick, it covers a hundred square meters.
You would need 25 (5x5).