What is the number of square tiles needed to cover a rectangular surface of 4m by 2m if the length of each side of the tile is 10cm?

Answer 1

Assuming the tile width is physically slightly less than 10cm so that when placed at 10 cm intervals there is room for grout between the tiles:

convert to same measurements and do the calculations:

1 m = 100 cm

→ 4 m = 4 × 100 cm = 400 cm

→ 2 m = 2 × 100 cm = 200 cm

→ the surface is 400 cm by 200 cm

400 cm ÷ 10 cm = 40 tiles across the surface in a row

200 cm ÷ 10 cm = 20 rows of tiles down the surface

→ need 40 × 20 = 800 tiles.

(You should buy a few more to allow for breakages.)

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There are two approaches to the this problem.

The one I have used above assumes the objects being used to fill the space cannot be broken down; it is the method you should use if you have an area (or volume) which needs to be filled with similar objects which cannot be broken down, eg packing tins in an outer crate for delivery - you may end up with unused space.

In a mathematical problem dressed up as a tiling problem (like this question) it is very unlikely that the tiles will not fit exactly in the space; in real life the opposite is true and you will require some part tiles to complete the tiling - it is usually best to always round UP (eg 5.2 would round up to 6) when finding how many tiles fit along each edge, calculate the number of tiles based on the rounded numbers and buy at least that number.

An alternative method which can be used WHEN the objects being used to fill the space may be broken down is to calculate the area (or volume) of the space and divide it by the area (or volume) of one object.

Answer 2

It is 800 - assuming there is no space for grouting.