You first need to find out what the pieces are. 12 mm is a measure of length. Length, by itself cannot be converted to an equivalent mass.
You have specified three dimensions. A rectangular area will have a length and a width. If your length is 90m, is the width 25mm or 12mm? I can't make sense of this as it is.
I think you can make 12 pieces at most
18 pieces
Impossible
12mm = 1.2cm
5
1 gigameter (Gm) is 1e+12mm
about how many pieces of pie did you eat? what about the rest of the year ?!
2
One to Six
Neither mass nor weight can be converted to length.
If you have 16 yards you can't make a 25 yard long piece. I think you meant how many 25 FEET long pieces. There are 3 feet in one yard. Figure it out.