Tiling

The Wilsons want to build a square patio in their backyard using square tiles. They bought 200 tiles that were 30 cm by 30 cm. What are the dimensions of the largest square patio they can make?

Extension
If the shape of the tiles was a quadrilateral other than a square, but each tile still maintained the area of 900 square cm, how would your answer to the previous question change? Assume that the tiles are laid out so that there aren’t any gaps or overlaps on the patio surface.