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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 903 · 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. 1.46 − 29 =
  2. 2.82 − 19 =
  3. 3.108 − 29 =
  4. 4.88 − 29 =
  5. 5.614 + 99 =
  6. 6.66 + 29 =
  7. 7.18 + 29 =
  8. 8.48 + 19 =
  9. 9.287 + 99 =
  10. 10.34 + 9 =
  11. 11.51 − 19 =
  12. 12.251 − 99 =
  13. 13.62 + 19 =
  14. 14.633 + 99 =
  15. 15.28 + 9 =
  16. 16.46 − 19 =
  17. 17.546 + 99 =
  18. 18.582 − 99 =
  19. 19.59 + 29 =
  20. 20.27 − 19 =
  21. 21.28 + 29 =
  22. 22.27 + 29 =
  23. 23.21 − 9 =
  24. 24.41 − 19 =
  25. 25.61 − 19 =
  26. 26.762 + 99 =
  27. 27.28 + 19 =
  28. 28.38 + 29 =
  29. 29.73 − 9 =
  30. 30.506 + 99 =
  31. 31.74 − 29 =
  32. 32.202 + 99 =
  33. 33.75 + 19 =
  34. 34.72 − 19 =
  35. 35.129 + 99 =
  36. 36.57 + 9 =
  37. 37.29 + 29 =
  38. 38.216 + 99 =
  39. 39.840 − 99 =
  40. 40.54 + 29 =

Answer key

  1. 17
  2. 63
  3. 79
  4. 59
  5. 713
  6. 95
  7. 47
  8. 67
  9. 386
  10. 43
  11. 32
  12. 152
  13. 81
  14. 732
  15. 37
  16. 27
  17. 645
  18. 483
  19. 88
  20. 8
  21. 57
  22. 56
  23. 12
  24. 22
  25. 42
  26. 861
  27. 47
  28. 67
  29. 64
  30. 605
  31. 45
  32. 301
  33. 94
  34. 53
  35. 228
  36. 66
  37. 58
  38. 315
  39. 741
  40. 83

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