1.OA.8

Determine the unknown whole number in an addition or subtraction equation relating three whole numbers. For example, determine the unknown number that makes the equation true in each of the equations 8 + ? = 11, 5 = _ - 3, 6 + 6 = _.

1. Addition chain: 4 + 1 = 5, 5 + 2 = ?
2. Addition chain: 2 + 2 = 4, 4 + 1 = ?
3. Addition chain: 3 + 2 = 5, 5 + 1 = ?
4. Number Detectives: ? + 5 = 11
5. Number Detectives: 9 + 5 = ?
6. Number Detectives: 6 + ? = 9
7. Use the Pattern: 4+3, +4, +5
8. Use the Pattern: 12+1, +2, +3
9. Number Detectives: ?+5 = 15
10. Addition Chain: 5 + 3 = ? + 3 = ?
11. Addition Chain: 6 + 4 = ? + 5 = ?
12. Addition Chain: 2 + 4 = ? + 5 = ?
13. Addition Chain: 3 + 9 = ? + 1 = ?
14. Addition Chain: 4 + 3 = ? + 5 = ?
15. Number Detectives: 12 + 3 = ?
16. Number Detectives: 9 + ? = 15
17. Number Detectives: 8 + ? = 15
18. Use the Pattern: 4+0, +10, +20
19. Use the Pattern: 5+0, +10, +20
20. Use the Pattern: 7+0, +10, +20
21. Use the Pattern: 6+0, +10, +20
22. Use the Pattern: 3+0, +10, +20
23. Use the Pattern: 9+0, +10, +20
24. Number Detectives: 10 + 27 = ?
25. Use the Pattern: 5+4,15+4,25+4
26. Use the Pattern: 6+4,16+4,26+4
27. Number detectives ? -3 = 11
28. Number detectives 18 -10 = ?
29. Number detectives 17 -? = 5
30. Use the pattern: 8 - 4, - 3, - 2
31. Use the pattern: 6 - 6, - 5, - 4
32. Subtraction chain 20 - 3 = 17, 17 - 3 = ?
33. Subtraction chain 20 - 6 = 14, 14 - 5 = ?
34. Subtraction chain 20 - 5 = 15, 15 - 2 = ?
35. Subtraction chain 20 - 9 = 11, 11 - 3 = ?