Across
- 7. used letters to represent numbers
- 8. developed the Ionic number system
- 10. wrote their numbers on clay tablets
- 12. copied their number system from the Greeks
- 13. wrote numbers vertically from top to bottom
Down
- 1. used knotted rope to record numbers
- 2. built the pyramids
- 3. used wedges to represent numbers
- 4. marks notched into bone
- 5. used pictures to represent numbers
- 6. used a shell to represent zero
- 9. represented five to the Mayans
- 11. knotted ropes