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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 29 · 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. 1.52 + 9 =
  2. 2.49 + 29 =
  3. 3.24 + 29 =
  4. 4.213 − 99 =
  5. 5.23 − 9 =
  6. 6.12 + 19 =
  7. 7.40 − 29 =
  8. 8.218 + 99 =
  9. 9.61 − 19 =
  10. 10.30 + 9 =
  11. 11.59 + 9 =
  12. 12.430 − 99 =
  13. 13.76 + 19 =
  14. 14.75 − 29 =
  15. 15.66 + 9 =
  16. 16.48 − 29 =
  17. 17.53 − 9 =
  18. 18.59 − 9 =
  19. 19.886 − 99 =
  20. 20.138 + 99 =
  21. 21.428 − 99 =
  22. 22.67 + 19 =
  23. 23.85 − 9 =
  24. 24.19 − 9 =
  25. 25.48 + 29 =
  26. 26.73 − 29 =
  27. 27.200 − 99 =
  28. 28.513 − 99 =
  29. 29.40 + 29 =
  30. 30.69 − 19 =
  31. 31.78 − 9 =
  32. 32.71 − 19 =
  33. 33.598 + 99 =
  34. 34.625 + 99 =
  35. 35.22 + 19 =
  36. 36.28 − 19 =
  37. 37.26 − 9 =
  38. 38.439 + 99 =
  39. 39.70 − 29 =
  40. 40.238 − 99 =

Answer key

  1. 61
  2. 78
  3. 53
  4. 114
  5. 14
  6. 31
  7. 11
  8. 317
  9. 42
  10. 39
  11. 68
  12. 331
  13. 95
  14. 46
  15. 75
  16. 19
  17. 44
  18. 50
  19. 787
  20. 237
  21. 329
  22. 86
  23. 76
  24. 10
  25. 77
  26. 44
  27. 101
  28. 414
  29. 69
  30. 50
  31. 69
  32. 52
  33. 697
  34. 724
  35. 41
  36. 9
  37. 17
  38. 538
  39. 41
  40. 139

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