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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 286 · 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. 1.19 + 29 =
  2. 2.296 + 99 =
  3. 3.13 + 9 =
  4. 4.102 − 29 =
  5. 5.47 − 29 =
  6. 6.76 + 29 =
  7. 7.724 − 99 =
  8. 8.60 − 9 =
  9. 9.37 + 9 =
  10. 10.25 + 29 =
  11. 11.70 − 9 =
  12. 12.37 − 19 =
  13. 13.49 + 9 =
  14. 14.278 + 99 =
  15. 15.46 + 19 =
  16. 16.56 + 19 =
  17. 17.30 − 9 =
  18. 18.165 + 99 =
  19. 19.65 + 9 =
  20. 20.507 − 99 =
  21. 21.48 + 19 =
  22. 22.73 + 19 =
  23. 23.40 + 9 =
  24. 24.369 + 99 =
  25. 25.47 − 9 =
  26. 26.42 − 19 =
  27. 27.523 − 99 =
  28. 28.610 + 99 =
  29. 29.72 − 19 =
  30. 30.383 − 99 =
  31. 31.64 − 19 =
  32. 32.66 + 29 =
  33. 33.12 + 29 =
  34. 34.58 + 9 =
  35. 35.94 − 29 =
  36. 36.68 − 9 =
  37. 37.89 − 9 =
  38. 38.74 − 9 =
  39. 39.51 − 9 =
  40. 40.54 + 29 =

Answer key

  1. 48
  2. 395
  3. 22
  4. 73
  5. 18
  6. 105
  7. 625
  8. 51
  9. 46
  10. 54
  11. 61
  12. 18
  13. 58
  14. 377
  15. 65
  16. 75
  17. 21
  18. 264
  19. 74
  20. 408
  21. 67
  22. 92
  23. 49
  24. 468
  25. 38
  26. 23
  27. 424
  28. 709
  29. 53
  30. 284
  31. 45
  32. 95
  33. 41
  34. 67
  35. 65
  36. 59
  37. 80
  38. 65
  39. 42
  40. 83

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