Math crossword puzzle

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Across
  1. 2. of operations
  2. 4. multiplication-process of multiplying
  3. 6. Algebra - letters representing numbers
  4. 7. of a whole
  5. 9. for making calculation
Down
  1. 1. numbers
  2. 3. is divided
  3. 5. line through the center of the circle
  4. 8. Addition - combining to or more