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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 39 · 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. 1.16 + 9 =
  2. 2.36 − 9 =
  3. 3.60 − 19 =
  4. 4.166 − 99 =
  5. 5.32 + 19 =
  6. 6.45 − 29 =
  7. 7.78 − 9 =
  8. 8.370 − 99 =
  9. 9.610 + 99 =
  10. 10.448 + 99 =
  11. 11.213 + 99 =
  12. 12.75 + 9 =
  13. 13.61 − 19 =
  14. 14.58 + 19 =
  15. 15.44 + 9 =
  16. 16.428 + 99 =
  17. 17.13 + 9 =
  18. 18.24 + 19 =
  19. 19.62 − 9 =
  20. 20.63 + 29 =
  21. 21.89 − 29 =
  22. 22.404 − 99 =
  23. 23.506 + 99 =
  24. 24.50 + 29 =
  25. 25.68 + 9 =
  26. 26.388 + 99 =
  27. 27.481 + 99 =
  28. 28.78 + 29 =
  29. 29.60 + 29 =
  30. 30.43 − 9 =
  31. 31.99 − 29 =
  32. 32.82 − 9 =
  33. 33.20 + 29 =
  34. 34.224 + 99 =
  35. 35.43 − 19 =
  36. 36.71 − 9 =
  37. 37.54 − 19 =
  38. 38.31 − 9 =
  39. 39.600 − 99 =
  40. 40.190 + 99 =

Answer key

  1. 25
  2. 27
  3. 41
  4. 67
  5. 51
  6. 16
  7. 69
  8. 271
  9. 709
  10. 547
  11. 312
  12. 84
  13. 42
  14. 77
  15. 53
  16. 527
  17. 22
  18. 43
  19. 53
  20. 92
  21. 60
  22. 305
  23. 605
  24. 79
  25. 77
  26. 487
  27. 580
  28. 107
  29. 89
  30. 34
  31. 70
  32. 73
  33. 49
  34. 323
  35. 24
  36. 62
  37. 35
  38. 22
  39. 501
  40. 289

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