Brain teaser

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Across
  1. 1. A number that divides exactly into another
  2. 3. A comparison using the words like or as
  3. 5. A word that means the opposite of another word
  4. 7. Describing something as if it were something else
  5. 9. The capacity to do work measured in joules
  6. 13. The central idea or message in a text
  7. 14. Two or more atoms bonded together
  8. 15. The steepness of a line on a graph
Down
  1. 2. Reviewing studied material before an exam
  2. 4. When a shape is a perfect mirror image of itself
  3. 6. Branch of maths using letters to represent unknowns
  4. 8. A number divisible only by itself and one
  5. 10. A comparison of two quantities
  6. 11. A pure substance made of only one type of atom
  7. 12. A whole number positive negative or zero