How many 20cm x 20cm tiles it would take to tile the floor and three
sides of a shower stall.  The stall has square floot, which is 16
square feet, and five-foot walls?  And what is the purpose for
order-of-magnitude calculations?

Can you please show me the work so I can see how it is done?

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Clarification of Question by mocha28-ga on 06 Dec 2005 21:07 PST

What is the area of a 20cm X 20cm tile?

Hi Mocha,
To solve the problem you don't really need to know the area of a tile,
just that one inch equals 2.54 cm.  The floor of the showerstall is
121.92 cm on each side.  With grouting (probably not to be
considered), 36 tiles would fit nicely, but without grouting you are
going to need some little pieces.  The same applies for the walls.  I
don't know whether the solution considers how many of the pieces can
be cut from one tile.

Hello Myoarin-ga,
    I see where you are coming from but it should take over 100 tiles
to do the floor that is 16 square feet and also do the 3 five foot
walls not just 36 tiles to cover the whole area at hand.  Do you see
where I came coming from?

Mocha,
100 square tiles would cover an area 10 x 10 tiles, each 20cm on the
side, so the side of the square they would cover would be 200cm long,
considerably more than the 121.92 cm side (= 4 ft) of the floor of the
shower stall.

OH, I quess you are saying that it would take more than 100 tiles to
do the whole job.  Yes you are right.  I was explaining just how many
tiles are needed for the floor.

Now I understand that this is not a homework assignment as I first
thought, which is why I didn't answer completely before.

The walls are 152.4 cm high, that will be 7 tiles plus 12.4 cm.  Now
it depends on how accurate your 4 by 4 ft and 4 by 5 ft measurements
are and also the width of the grouting, but with five lines of
grouting on the floor, the 6 x 6 should  work fine  - about 2 mm
lines.
I am no craftsman, but I believe the floor tiles should extend under
those on the wall, so you can subtract the thickness of the tiles from
the 152.4 cm height, and again the 7 lines of grouting should account
for at least 1.4 cm, so I estimate that you need half a tile (10x20
cm) to complete the 5 ft height.

SO, you need 36 tiles for the floor and 6x7 1/2 for each wall (=45),
but let's say 6x8 = 48, x 3 plus the floor for a total of 180 tiles.
Better get a few more.

Does that make sense?
Regards, Myoarin

Hello Myoarin-ga,
 Your conclusions are close to mine.  I had estimated 186 tiles to
cover at my first guess cause it just amazed me to find out. You are
so correct about the walls having an extra 1/2 of a tile to cover the
remining wall. But last night I tried to do the experience myself with
my house wall this is what I came up with to determine how many tiles
it would take to cover the walls. 5ft equals to 152.40 cm which is
converted to 60 inches per side (4) equaling 240 total inches of area
in the tile (right).  I grab a 12 inch ruler and divided 60 inches
into 12 inches and I will have to use the ruler 5 times up the wall
and across to get 240 inches of a square wall.  Figuring that each
tile will be 13 1/2 inches for each side.  That will give me 4 1/2
tiles needed  to cover one side and across and then fill in the rest. 
Do, my second guess came out to that I will need 18 tiles to cover one
wall x 3.  Does this make any sense to you?  But then it came out to
be a total of 67 tiles need (throw a few extra ones in there)

Hi Mocha,
Your first guess was right, however you arrived at it.  
After that, I had to grin a little at your explanation; reminded me of
how my wife  tried to calculate the material needed for new window
sills:  she added the widths of the windows, and the depths of the
various sills, and then multiplied the two sums.  The result a large
multiple of the correct answer.
But anyway: 20 cm is 20 / 2.54  = 7.874 inches, not 13 1/2 inches 
(Old English measure of a "hand" is 4 inches, about the width of your
hand between the top knuckles of the index and little finger.  This is
about 10 cm.  You might keep this in mind when dealing with metric
measurements.)
So whatever you calculated with the 13 1/2 inches is wrong.
The shower floor will be 6x6 tiles and the sides will be 6x8 (6x7.5,
but we have to plan that after breaking the last tile down the 20x10
cm  the rest of those tiles will be unusable.
You may have a problem with the vertical corners between the walls, if
for some reason the tiling on them must be precisely 4 ft in width.

Good luck, Myoarin