Math
posted by Arch .
A rectangular garden of dimension 12m by 9m is enclosed by a uniform concrete walk 1.5m wide. If the walk is to be tiled, how many 30cm square tile are needed to tile the entire walk?

The area of the walk is 15*12  12*9 = 72m^2
72m^2 / (.3m)^2 = 800 tiles
Or, you can figure 5 tiles to cross the width of the walk. The garden is 12/.3 = 40 tiles long and 9/.3 = 30 tiles wide.
You will need
two strips of 40x5 on the long side
two strips of 30x5 on the short side
4 corners of 5x5
400+300+100 = 800