Math cross word

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Across
  1. 3. Repeated Addition
  2. 6. The space within an enclosure
  3. 7. The perimeter of a circle
  4. 8. Positive and Negative numbers
Down
  1. 1. the operation of seperating a part from a whole
  2. 2. The length of a line through a circle
  3. 4. The boundary of an area
  4. 5. Parts of a whole
  5. 6. Replacing a number with an alphabet