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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 30 · 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. 1.17 + 19 =
  2. 2.17 + 9 =
  3. 3.25 + 9 =
  4. 4.48 − 9 =
  5. 5.63 − 19 =
  6. 6.91 − 19 =
  7. 7.207 − 99 =
  8. 8.642 + 99 =
  9. 9.63 − 29 =
  10. 10.472 − 99 =
  11. 11.50 − 9 =
  12. 12.43 + 9 =
  13. 13.71 + 9 =
  14. 14.68 + 9 =
  15. 15.54 − 29 =
  16. 16.66 − 19 =
  17. 17.48 − 29 =
  18. 18.29 + 9 =
  19. 19.12 + 9 =
  20. 20.579 − 99 =
  21. 21.50 + 9 =
  22. 22.647 + 99 =
  23. 23.65 − 29 =
  24. 24.60 + 29 =
  25. 25.93 − 29 =
  26. 26.15 + 29 =
  27. 27.36 + 19 =
  28. 28.32 + 9 =
  29. 29.65 + 29 =
  30. 30.39 − 19 =
  31. 31.45 − 9 =
  32. 32.21 + 19 =
  33. 33.63 + 19 =
  34. 34.357 − 99 =
  35. 35.36 − 9 =
  36. 36.49 + 19 =
  37. 37.619 − 99 =
  38. 38.156 − 99 =
  39. 39.87 − 19 =
  40. 40.119 + 99 =

Answer key

  1. 36
  2. 26
  3. 34
  4. 39
  5. 44
  6. 72
  7. 108
  8. 741
  9. 34
  10. 373
  11. 41
  12. 52
  13. 80
  14. 77
  15. 25
  16. 47
  17. 19
  18. 38
  19. 21
  20. 480
  21. 59
  22. 746
  23. 36
  24. 89
  25. 64
  26. 44
  27. 55
  28. 41
  29. 94
  30. 20
  31. 36
  32. 40
  33. 82
  34. 258
  35. 27
  36. 68
  37. 520
  38. 57
  39. 68
  40. 218

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