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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 862 · 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. 1.297 + 99 =
  2. 2.72 + 9 =
  3. 3.68 + 9 =
  4. 4.57 + 19 =
  5. 5.31 + 9 =
  6. 6.775 + 99 =
  7. 7.39 − 29 =
  8. 8.77 − 9 =
  9. 9.41 − 19 =
  10. 10.13 − 9 =
  11. 11.275 + 99 =
  12. 12.33 + 29 =
  13. 13.75 + 9 =
  14. 14.20 − 9 =
  15. 15.47 − 9 =
  16. 16.107 + 99 =
  17. 17.35 + 9 =
  18. 18.63 − 19 =
  19. 19.66 + 9 =
  20. 20.66 + 19 =
  21. 21.23 − 9 =
  22. 22.79 + 29 =
  23. 23.65 + 9 =
  24. 24.49 − 19 =
  25. 25.26 + 29 =
  26. 26.58 + 29 =
  27. 27.69 + 9 =
  28. 28.368 + 99 =
  29. 29.27 − 19 =
  30. 30.59 + 19 =
  31. 31.55 + 19 =
  32. 32.361 − 99 =
  33. 33.71 + 9 =
  34. 34.613 − 99 =
  35. 35.204 − 99 =
  36. 36.58 + 19 =
  37. 37.38 − 29 =
  38. 38.42 − 9 =
  39. 39.279 + 99 =
  40. 40.45 + 29 =

Answer key

  1. 396
  2. 81
  3. 77
  4. 76
  5. 40
  6. 874
  7. 10
  8. 68
  9. 22
  10. 4
  11. 374
  12. 62
  13. 84
  14. 11
  15. 38
  16. 206
  17. 44
  18. 44
  19. 75
  20. 85
  21. 14
  22. 108
  23. 74
  24. 30
  25. 55
  26. 87
  27. 78
  28. 467
  29. 8
  30. 78
  31. 74
  32. 262
  33. 80
  34. 514
  35. 105
  36. 77
  37. 9
  38. 33
  39. 378
  40. 74

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