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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 88 · 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. 1.66 − 29 =
  2. 2.38 + 19 =
  3. 3.29 + 29 =
  4. 4.19 − 9 =
  5. 5.20 + 19 =
  6. 6.52 + 19 =
  7. 7.69 − 19 =
  8. 8.40 − 29 =
  9. 9.15 − 9 =
  10. 10.81 − 19 =
  11. 11.617 + 99 =
  12. 12.15 + 19 =
  13. 13.14 + 9 =
  14. 14.53 − 29 =
  15. 15.68 + 9 =
  16. 16.41 + 29 =
  17. 17.66 − 9 =
  18. 18.55 − 19 =
  19. 19.87 − 19 =
  20. 20.69 + 9 =
  21. 21.22 + 19 =
  22. 22.331 − 99 =
  23. 23.75 + 9 =
  24. 24.58 + 29 =
  25. 25.30 + 29 =
  26. 26.17 + 9 =
  27. 27.47 + 19 =
  28. 28.91 − 29 =
  29. 29.71 + 29 =
  30. 30.79 + 29 =
  31. 31.886 − 99 =
  32. 32.27 + 9 =
  33. 33.91 − 19 =
  34. 34.67 − 9 =
  35. 35.361 − 99 =
  36. 36.394 − 99 =
  37. 37.88 − 9 =
  38. 38.217 + 99 =
  39. 39.77 + 29 =
  40. 40.65 + 29 =

Answer key

  1. 37
  2. 57
  3. 58
  4. 10
  5. 39
  6. 71
  7. 50
  8. 11
  9. 6
  10. 62
  11. 716
  12. 34
  13. 23
  14. 24
  15. 77
  16. 70
  17. 57
  18. 36
  19. 68
  20. 78
  21. 41
  22. 232
  23. 84
  24. 87
  25. 59
  26. 26
  27. 66
  28. 62
  29. 100
  30. 108
  31. 787
  32. 36
  33. 72
  34. 58
  35. 262
  36. 295
  37. 79
  38. 316
  39. 106
  40. 94

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