Maths Problem

Well...you have one problem here.....

The total floor area = 186 * 207 = 38,502 cm^2

But.....the total area of the tiles = 89 * 5 * 5   = only 2225 cm^2

So.....you don't have enough tiles to cover the area no matter how they are arranged

but 89 squares each have sides of 5cm are placed on a floor 18.6cm wide and 20.7cm long, how many full squares are used and how many are cut and how many are not used

i get floor area to be 385.02cm squared

There weren't any decimals in the "186" and "207"  of your original question !!!!!

Assuming that the 18.6 is the width and the 20.7 is the length

First.....we would have 4 rows of 3 tiles each in a row  = 12 tiles  = 300 cm^2

Then....we could tack a tile on the end of each row that had cut width of [ 18.6 - 15] = 3.6cm

Thus 4 tiles would be cut, each having a width of 3.6cm and a length of 5cm

And the total area of these = 4 * 3.6 * 5 = 72cm^2

And, at the bottom.....we would have 3 more cut tiles each having a width of 5 cm  and a cut length of .7cm.......and the total area of these = 3* 5 * .7 = 10.5 cm^2

Finally....there is one tile remaining at a corner that has a cut width and length of  3.6cm by .7 cm = 2.52 cm^2

So....the total area covered  = 300 + 72 + 10.5 + 2.52  = 385.02 cm^2

And we would use 12 whole tiles plus  [4 + 3 + 1]  = 8 cut tiles

So 20 tiles are used and 89 - 20   = 69 are not