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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 846 · 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. 1.67 − 29 =
  2. 2.28 + 29 =
  3. 3.62 + 19 =
  4. 4.66 − 29 =
  5. 5.51 − 19 =
  6. 6.58 + 29 =
  7. 7.77 + 9 =
  8. 8.76 − 19 =
  9. 9.43 − 9 =
  10. 10.28 − 19 =
  11. 11.23 − 9 =
  12. 12.85 − 29 =
  13. 13.95 − 19 =
  14. 14.36 − 29 =
  15. 15.98 − 19 =
  16. 16.49 + 29 =
  17. 17.89 − 29 =
  18. 18.555 − 99 =
  19. 19.73 − 29 =
  20. 20.282 + 99 =
  21. 21.22 − 19 =
  22. 22.52 + 29 =
  23. 23.79 − 19 =
  24. 24.12 + 9 =
  25. 25.58 + 9 =
  26. 26.489 + 99 =
  27. 27.534 − 99 =
  28. 28.46 − 9 =
  29. 29.84 − 29 =
  30. 30.78 + 29 =
  31. 31.64 + 29 =
  32. 32.364 − 99 =
  33. 33.53 − 19 =
  34. 34.17 + 29 =
  35. 35.46 − 19 =
  36. 36.197 + 99 =
  37. 37.28 + 19 =
  38. 38.64 − 29 =
  39. 39.52 − 29 =
  40. 40.39 + 9 =

Answer key

  1. 38
  2. 57
  3. 81
  4. 37
  5. 32
  6. 87
  7. 86
  8. 57
  9. 34
  10. 9
  11. 14
  12. 56
  13. 76
  14. 7
  15. 79
  16. 78
  17. 60
  18. 456
  19. 44
  20. 381
  21. 3
  22. 81
  23. 60
  24. 21
  25. 67
  26. 588
  27. 435
  28. 37
  29. 55
  30. 107
  31. 93
  32. 265
  33. 34
  34. 46
  35. 27
  36. 296
  37. 47
  38. 35
  39. 23
  40. 48

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