The walls of a bathroom 2,5 m long, 2,05 m wide and 3 m high are to be covered with
tiles, each 15 cm by 15 cm. If a saving of
108 tiles is made on doors and windows,
how many tiles will be needed altogether?
Note that some tiles will have to be cut.)

The number of tiles needed is 1.105. tiles

Step-by-step explanation:

The given data on the dimensions of the bathroom wall are;

The length, l = 2.5 m

The width, w = 2.05 m

The height, h = 3 m

The dimension of the tiles with which the walls are to be covered = 15 cm by 15 cm

The dimensions of the tiles in meters = 0.15 m by 0.15 m

The number of tiles savings made on the doors and windows of the bathroom = 108 tiles

Let 'A' represent the surface area of the bathroom wall, we have;

A = h·w + h·w + l·h + l·h = 2·h·w + 2·l·h =  2·h·(w + l)

∴ A = 2 × 3 m (2.5 m + 2.05 m) = 27.3 m²

The surface area per tile, Tₐ = 0.15  × 0.15  = 0.0225

∴ Tₐ = 0.0225 m²/tile

The number of tiles needed, n = A/Tₐ - 108 tiles

∴ n = 27.3 m²/(0.0225 m²/tile - 108 tiles  = tiles = 1.105. tiles

The number of tiles needed, n = 1.105. tiles.