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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 324 · 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. 1.357 − 99 =
  2. 2.88 − 9 =
  3. 3.37 + 9 =
  4. 4.104 − 29 =
  5. 5.66 + 9 =
  6. 6.97 − 29 =
  7. 7.330 + 99 =
  8. 8.361 − 99 =
  9. 9.597 − 99 =
  10. 10.32 − 19 =
  11. 11.35 + 29 =
  12. 12.434 + 99 =
  13. 13.232 − 99 =
  14. 14.27 − 19 =
  15. 15.54 + 19 =
  16. 16.108 − 29 =
  17. 17.50 − 29 =
  18. 18.55 + 29 =
  19. 19.54 + 9 =
  20. 20.28 + 19 =
  21. 21.45 − 29 =
  22. 22.83 − 29 =
  23. 23.67 − 19 =
  24. 24.17 − 9 =
  25. 25.15 + 9 =
  26. 26.403 + 99 =
  27. 27.14 + 19 =
  28. 28.83 − 9 =
  29. 29.890 − 99 =
  30. 30.13 + 9 =
  31. 31.552 + 99 =
  32. 32.12 + 19 =
  33. 33.58 − 19 =
  34. 34.33 + 9 =
  35. 35.86 − 9 =
  36. 36.12 + 9 =
  37. 37.166 − 99 =
  38. 38.24 − 9 =
  39. 39.785 + 99 =
  40. 40.541 − 99 =

Answer key

  1. 258
  2. 79
  3. 46
  4. 75
  5. 75
  6. 68
  7. 429
  8. 262
  9. 498
  10. 13
  11. 64
  12. 533
  13. 133
  14. 8
  15. 73
  16. 79
  17. 21
  18. 84
  19. 63
  20. 47
  21. 16
  22. 54
  23. 48
  24. 8
  25. 24
  26. 502
  27. 33
  28. 74
  29. 791
  30. 22
  31. 651
  32. 31
  33. 39
  34. 42
  35. 77
  36. 21
  37. 67
  38. 15
  39. 884
  40. 442

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