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Adding 9, 19 and 99 Mental Maths Worksheet

Mental maths lesson 4: Add and take away 9, 19 and 99 · Set 755 · 40 questions
TalentJR

How to do it in your head (Round and adjust): Add 9, 19, 99: add 10, 20, 100, then take 1 away. Take away 9, 19, 99: take away 10, 20, 100, then add 1 back. Ask yourself: did I use too much or too little?

NameDateTime takenScore ___ / 40
  1. 1.24 + 19 =
  2. 2.51 + 9 =
  3. 3.516 + 99 =
  4. 4.94 − 29 =
  5. 5.59 − 9 =
  6. 6.197 − 99 =
  7. 7.58 − 9 =
  8. 8.12 + 9 =
  9. 9.82 − 9 =
  10. 10.104 − 29 =
  11. 11.789 − 99 =
  12. 12.25 + 29 =
  13. 13.96 − 19 =
  14. 14.79 − 19 =
  15. 15.43 − 9 =
  16. 16.73 − 9 =
  17. 17.66 − 9 =
  18. 18.34 + 29 =
  19. 19.17 − 9 =
  20. 20.68 + 29 =
  21. 21.46 − 9 =
  22. 22.58 + 9 =
  23. 23.419 + 99 =
  24. 24.38 − 9 =
  25. 25.305 + 99 =
  26. 26.261 − 99 =
  27. 27.55 − 19 =
  28. 28.39 + 19 =
  29. 29.31 − 9 =
  30. 30.230 − 99 =
  31. 31.54 − 9 =
  32. 32.54 − 19 =
  33. 33.48 − 9 =
  34. 34.32 + 9 =
  35. 35.84 − 9 =
  36. 36.31 + 29 =
  37. 37.58 − 19 =
  38. 38.50 − 29 =
  39. 39.22 − 9 =
  40. 40.33 + 29 =

Answer key

  1. 43
  2. 60
  3. 615
  4. 65
  5. 50
  6. 98
  7. 49
  8. 21
  9. 73
  10. 75
  11. 690
  12. 54
  13. 77
  14. 60
  15. 34
  16. 64
  17. 57
  18. 63
  19. 8
  20. 97
  21. 37
  22. 67
  23. 518
  24. 29
  25. 404
  26. 162
  27. 36
  28. 58
  29. 22
  30. 131
  31. 45
  32. 35
  33. 39
  34. 41
  35. 75
  36. 60
  37. 39
  38. 21
  39. 13
  40. 62

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