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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 427 · 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. 1.69 + 19 =
  2. 2.638 + 99 =
  3. 3.297 − 99 =
  4. 4.95 − 29 =
  5. 5.70 + 19 =
  6. 6.66 − 29 =
  7. 7.65 + 29 =
  8. 8.682 − 99 =
  9. 9.23 − 19 =
  10. 10.159 + 99 =
  11. 11.28 + 19 =
  12. 12.497 + 99 =
  13. 13.57 + 29 =
  14. 14.63 − 29 =
  15. 15.40 − 19 =
  16. 16.566 − 99 =
  17. 17.745 + 99 =
  18. 18.52 − 9 =
  19. 19.58 − 29 =
  20. 20.35 − 29 =
  21. 21.85 − 19 =
  22. 22.38 + 9 =
  23. 23.32 − 29 =
  24. 24.22 + 9 =
  25. 25.53 − 9 =
  26. 26.29 − 9 =
  27. 27.35 − 9 =
  28. 28.44 + 9 =
  29. 29.440 + 99 =
  30. 30.37 − 29 =
  31. 31.79 + 29 =
  32. 32.74 + 29 =
  33. 33.91 − 19 =
  34. 34.26 + 19 =
  35. 35.46 + 19 =
  36. 36.80 − 9 =
  37. 37.62 + 19 =
  38. 38.438 + 99 =
  39. 39.198 + 99 =
  40. 40.53 + 9 =

Answer key

  1. 88
  2. 737
  3. 198
  4. 66
  5. 89
  6. 37
  7. 94
  8. 583
  9. 4
  10. 258
  11. 47
  12. 596
  13. 86
  14. 34
  15. 21
  16. 467
  17. 844
  18. 43
  19. 29
  20. 6
  21. 66
  22. 47
  23. 3
  24. 31
  25. 44
  26. 20
  27. 26
  28. 53
  29. 539
  30. 8
  31. 108
  32. 103
  33. 72
  34. 45
  35. 65
  36. 71
  37. 81
  38. 537
  39. 297
  40. 62

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