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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 383 · 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. 1.98 − 19 =
  2. 2.543 + 99 =
  3. 3.34 − 19 =
  4. 4.43 − 29 =
  5. 5.60 − 29 =
  6. 6.59 + 9 =
  7. 7.32 + 9 =
  8. 8.65 − 29 =
  9. 9.38 − 9 =
  10. 10.25 + 19 =
  11. 11.53 + 9 =
  12. 12.54 + 29 =
  13. 13.231 + 99 =
  14. 14.36 + 19 =
  15. 15.38 − 19 =
  16. 16.75 + 9 =
  17. 17.53 + 19 =
  18. 18.63 + 29 =
  19. 19.46 − 19 =
  20. 20.68 − 9 =
  21. 21.30 − 19 =
  22. 22.32 + 29 =
  23. 23.596 − 99 =
  24. 24.650 − 99 =
  25. 25.628 + 99 =
  26. 26.67 + 29 =
  27. 27.62 + 9 =
  28. 28.39 − 9 =
  29. 29.54 − 19 =
  30. 30.24 + 19 =
  31. 31.22 + 9 =
  32. 32.58 − 9 =
  33. 33.60 + 9 =
  34. 34.71 − 19 =
  35. 35.40 − 29 =
  36. 36.745 − 99 =
  37. 37.84 − 9 =
  38. 38.17 + 9 =
  39. 39.53 + 29 =
  40. 40.705 − 99 =

Answer key

  1. 79
  2. 642
  3. 15
  4. 14
  5. 31
  6. 68
  7. 41
  8. 36
  9. 29
  10. 44
  11. 62
  12. 83
  13. 330
  14. 55
  15. 19
  16. 84
  17. 72
  18. 92
  19. 27
  20. 59
  21. 11
  22. 61
  23. 497
  24. 551
  25. 727
  26. 96
  27. 71
  28. 30
  29. 35
  30. 43
  31. 31
  32. 49
  33. 69
  34. 52
  35. 11
  36. 646
  37. 75
  38. 26
  39. 82
  40. 606

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