Math Crossword puzzle

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Across
  1. 2. - average of numbers
  2. 4. - whole number and fraction combined
  3. 5. - a whole number whose only factors are 1 and itsel
  4. 7. - a fact or a rule written with mathematical symbols
  5. 9. - length of the line through the center of a circle
  6. 12. - numerator is greater than the denominator
  7. 14. - number below 0
  8. 15. - two or more numbers which have a sum
  9. 17. - two or more numbers with a operator
  10. 18. - turns an object
  11. 20. - decimal that never ends
Down
  1. 1. - changes the size of an object
  2. 3. - middle number
  3. 6. - events that happen at the same time
  4. 8. - most frequent number
  5. 10. - difference between the lowest and highest value
  6. 11. - how likely something is to happen
  7. 13. - first non-zero digit
  8. 16. - 3 sided polygon
  9. 19. - the space in an object