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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 983 · 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. 1.64 − 19 =
  2. 2.42 − 9 =
  3. 3.497 + 99 =
  4. 4.70 − 29 =
  5. 5.513 + 99 =
  6. 6.42 + 19 =
  7. 7.90 − 19 =
  8. 8.39 − 9 =
  9. 9.69 − 9 =
  10. 10.751 − 99 =
  11. 11.61 + 9 =
  12. 12.30 − 19 =
  13. 13.45 − 19 =
  14. 14.453 + 99 =
  15. 15.81 − 19 =
  16. 16.261 + 99 =
  17. 17.23 − 9 =
  18. 18.38 + 19 =
  19. 19.168 − 99 =
  20. 20.211 + 99 =
  21. 21.29 + 29 =
  22. 22.16 + 9 =
  23. 23.228 − 99 =
  24. 24.41 − 19 =
  25. 25.369 − 99 =
  26. 26.58 + 29 =
  27. 27.70 − 9 =
  28. 28.39 − 29 =
  29. 29.18 + 9 =
  30. 30.53 + 29 =
  31. 31.89 − 29 =
  32. 32.109 − 29 =
  33. 33.45 + 9 =
  34. 34.66 + 19 =
  35. 35.14 + 9 =
  36. 36.15 + 9 =
  37. 37.68 + 19 =
  38. 38.478 − 99 =
  39. 39.33 + 29 =
  40. 40.95 − 29 =

Answer key

  1. 45
  2. 33
  3. 596
  4. 41
  5. 612
  6. 61
  7. 71
  8. 30
  9. 60
  10. 652
  11. 70
  12. 11
  13. 26
  14. 552
  15. 62
  16. 360
  17. 14
  18. 57
  19. 69
  20. 310
  21. 58
  22. 25
  23. 129
  24. 22
  25. 270
  26. 87
  27. 61
  28. 10
  29. 27
  30. 82
  31. 60
  32. 80
  33. 54
  34. 85
  35. 23
  36. 24
  37. 87
  38. 379
  39. 62
  40. 66

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