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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 833 · 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. 1.336 − 99 =
  2. 2.28 − 9 =
  3. 3.85 − 29 =
  4. 4.112 + 99 =
  5. 5.68 + 9 =
  6. 6.153 + 99 =
  7. 7.40 − 29 =
  8. 8.84 − 19 =
  9. 9.76 − 19 =
  10. 10.26 + 19 =
  11. 11.35 + 19 =
  12. 12.13 − 9 =
  13. 13.279 − 99 =
  14. 14.743 − 99 =
  15. 15.30 − 9 =
  16. 16.15 + 19 =
  17. 17.225 − 99 =
  18. 18.117 + 99 =
  19. 19.19 + 19 =
  20. 20.47 + 29 =
  21. 21.671 − 99 =
  22. 22.73 − 9 =
  23. 23.570 − 99 =
  24. 24.103 − 29 =
  25. 25.71 + 29 =
  26. 26.69 + 9 =
  27. 27.30 + 19 =
  28. 28.56 − 9 =
  29. 29.19 + 9 =
  30. 30.65 + 19 =
  31. 31.35 + 9 =
  32. 32.61 − 9 =
  33. 33.23 + 29 =
  34. 34.24 + 19 =
  35. 35.62 − 29 =
  36. 36.17 + 9 =
  37. 37.79 + 9 =
  38. 38.185 + 99 =
  39. 39.39 − 29 =
  40. 40.663 − 99 =

Answer key

  1. 237
  2. 19
  3. 56
  4. 211
  5. 77
  6. 252
  7. 11
  8. 65
  9. 57
  10. 45
  11. 54
  12. 4
  13. 180
  14. 644
  15. 21
  16. 34
  17. 126
  18. 216
  19. 38
  20. 76
  21. 572
  22. 64
  23. 471
  24. 74
  25. 100
  26. 78
  27. 49
  28. 47
  29. 28
  30. 84
  31. 44
  32. 52
  33. 52
  34. 43
  35. 33
  36. 26
  37. 88
  38. 284
  39. 10
  40. 564

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