Tiles in the Garden

Tiles in the Garden

This is a view, from above, of my friend's garden. You see a black path and a square patch in the middle.

He wants to tile the square in the middle with tiles going straight across and down. He would also like to have the corner of a tile at each of the corners of the square.

Then it'll look like this;

So, we are off to help him. He has a good tile cutter to get the "part-tiles", so he'll be able to cut a tile into two or more pieces and use them all. But I said that we would fetch the tiles for him. How many do we need for the example above?

How many would we need for these two other garden square shapes that someone might like to have? How are you working it out?