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.
18 pieces
1.2 cm
1 gigameter (Gm) is 1e+12mm
12 millimeters = 1.2 centimetersEMDOG
2
6 peices make up a deckchair
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.
They make many arts like jars,plaques(flat pieces), Oracle bones, bone, turtle shell, or cattle scapulae pieces.
it takes over 100 peices
Direct Conversion Formula 12 mm* 1 in 25.4 mm = 0.4724409449 in
What? Have ever looked at a softball? There's two white pieces usally sewed together by red stitching.