math but nerdy -Jacob (NOT BY HIM)

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Across
  1. 3. the most important HISTORICAL element
  2. 7. does well with peroxide
  3. 11. medium weight
  4. 13. subnatica !!BELLOW ZERO!!
  5. 14. third grande masterpiece
  6. 15. this is america
  7. 16. all side are equal
  8. 19. the famous calculation
  9. 21. the most known table and built the universe
  10. 22. = l x w
  11. 23. 36 inches = this word
  12. 26. tiny winy weight
  13. 28. cheating device legend
  14. 29. 2D mix of shapes
  15. 31. happy happy happy
  16. 32. you can drink it.......yes.....you can
Down
  1. 1. the corner\side of a plane
  2. 2. 12 equals to a foot
  3. 4. mix and mix and mix and MIX
  4. 5. the decimal sibling
  5. 6. .'.'.'.'.'oh so fancy.'.'.'.'.'
  6. 8. repeated multiplication X2
  7. 9. the fraction sibling
  8. 10. 3D mix of shapes
  9. 12. BIG BOY weight
  10. 14. every thing in this crossword
  11. 16. repeated multiplication X3
  12. 17. M and C squared equal to it
  13. 18. two length + two width really EZ
  14. 20. this is pi followed by.....
  15. 24. more like master in pieces
  16. 25. = (l x w) x h :IN THAT ORDER
  17. 27. no equal at all
  18. 30. fancy yard