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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 380 · 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. 1.227 − 99 =
  2. 2.49 + 9 =
  3. 3.48 + 29 =
  4. 4.25 − 19 =
  5. 5.57 + 9 =
  6. 6.15 + 9 =
  7. 7.65 + 29 =
  8. 8.494 − 99 =
  9. 9.79 + 29 =
  10. 10.105 − 29 =
  11. 11.103 − 29 =
  12. 12.27 + 9 =
  13. 13.39 + 9 =
  14. 14.636 − 99 =
  15. 15.71 + 9 =
  16. 16.23 − 19 =
  17. 17.25 + 29 =
  18. 18.33 − 29 =
  19. 19.80 − 29 =
  20. 20.29 + 29 =
  21. 21.754 + 99 =
  22. 22.63 + 9 =
  23. 23.34 + 9 =
  24. 24.13 − 9 =
  25. 25.60 + 19 =
  26. 26.31 + 19 =
  27. 27.25 − 9 =
  28. 28.71 − 19 =
  29. 29.80 + 19 =
  30. 30.62 + 9 =
  31. 31.60 + 9 =
  32. 32.24 − 19 =
  33. 33.66 − 9 =
  34. 34.30 + 19 =
  35. 35.68 + 19 =
  36. 36.35 − 29 =
  37. 37.73 + 29 =
  38. 38.247 − 99 =
  39. 39.66 + 9 =
  40. 40.58 + 9 =

Answer key

  1. 128
  2. 58
  3. 77
  4. 6
  5. 66
  6. 24
  7. 94
  8. 395
  9. 108
  10. 76
  11. 74
  12. 36
  13. 48
  14. 537
  15. 80
  16. 4
  17. 54
  18. 4
  19. 51
  20. 58
  21. 853
  22. 72
  23. 43
  24. 4
  25. 79
  26. 50
  27. 16
  28. 52
  29. 99
  30. 71
  31. 69
  32. 5
  33. 57
  34. 49
  35. 87
  36. 6
  37. 102
  38. 148
  39. 75
  40. 67

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