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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 448 · 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. 1.65 − 9 =
  2. 2.36 + 9 =
  3. 3.58 − 29 =
  4. 4.77 + 9 =
  5. 5.471 − 99 =
  6. 6.31 + 9 =
  7. 7.65 + 29 =
  8. 8.28 + 9 =
  9. 9.28 + 19 =
  10. 10.54 + 9 =
  11. 11.248 − 99 =
  12. 12.56 + 9 =
  13. 13.388 + 99 =
  14. 14.452 − 99 =
  15. 15.51 − 9 =
  16. 16.66 − 29 =
  17. 17.78 − 19 =
  18. 18.36 + 19 =
  19. 19.17 + 29 =
  20. 20.24 + 19 =
  21. 21.39 + 19 =
  22. 22.55 + 19 =
  23. 23.52 + 29 =
  24. 24.13 + 29 =
  25. 25.14 + 9 =
  26. 26.53 + 29 =
  27. 27.37 + 29 =
  28. 28.689 + 99 =
  29. 29.607 − 99 =
  30. 30.32 + 9 =
  31. 31.217 + 99 =
  32. 32.69 + 9 =
  33. 33.553 − 99 =
  34. 34.86 − 9 =
  35. 35.641 − 99 =
  36. 36.67 + 9 =
  37. 37.98 − 19 =
  38. 38.871 − 99 =
  39. 39.586 − 99 =
  40. 40.45 + 19 =

Answer key

  1. 56
  2. 45
  3. 29
  4. 86
  5. 372
  6. 40
  7. 94
  8. 37
  9. 47
  10. 63
  11. 149
  12. 65
  13. 487
  14. 353
  15. 42
  16. 37
  17. 59
  18. 55
  19. 46
  20. 43
  21. 58
  22. 74
  23. 81
  24. 42
  25. 23
  26. 82
  27. 66
  28. 788
  29. 508
  30. 41
  31. 316
  32. 78
  33. 454
  34. 77
  35. 542
  36. 76
  37. 79
  38. 772
  39. 487
  40. 64

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