Mathematics

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Across
  1. 2. what is the predisessor of 2445
  2. 4. What is the successor of 2999 ?
  3. 5. What is the predisessor of 1501 ?
Down
  1. 1. predisessor of 6999 ?
  2. 2. What should we add to 500 become 2000 ?
  3. 3. Four thousand five hundred sixty seven?