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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 159 · 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. 1.52 + 9 =
  2. 2.297 + 99 =
  3. 3.794 − 99 =
  4. 4.552 + 99 =
  5. 5.108 − 29 =
  6. 6.34 − 29 =
  7. 7.13 − 9 =
  8. 8.113 + 99 =
  9. 9.43 − 29 =
  10. 10.17 − 9 =
  11. 11.164 + 99 =
  12. 12.41 + 9 =
  13. 13.69 + 9 =
  14. 14.126 + 99 =
  15. 15.64 − 29 =
  16. 16.80 + 29 =
  17. 17.53 + 19 =
  18. 18.70 − 29 =
  19. 19.65 + 19 =
  20. 20.58 − 29 =
  21. 21.76 + 29 =
  22. 22.54 − 19 =
  23. 23.40 + 9 =
  24. 24.51 + 29 =
  25. 25.421 − 99 =
  26. 26.242 + 99 =
  27. 27.103 − 29 =
  28. 28.28 + 9 =
  29. 29.672 + 99 =
  30. 30.41 + 19 =
  31. 31.33 − 19 =
  32. 32.50 + 19 =
  33. 33.15 + 19 =
  34. 34.44 + 9 =
  35. 35.15 + 9 =
  36. 36.109 − 29 =
  37. 37.61 + 19 =
  38. 38.90 − 19 =
  39. 39.60 + 19 =
  40. 40.42 + 9 =

Answer key

  1. 61
  2. 396
  3. 695
  4. 651
  5. 79
  6. 5
  7. 4
  8. 212
  9. 14
  10. 8
  11. 263
  12. 50
  13. 78
  14. 225
  15. 35
  16. 109
  17. 72
  18. 41
  19. 84
  20. 29
  21. 105
  22. 35
  23. 49
  24. 80
  25. 322
  26. 341
  27. 74
  28. 37
  29. 771
  30. 60
  31. 14
  32. 69
  33. 34
  34. 53
  35. 24
  36. 80
  37. 80
  38. 71
  39. 79
  40. 51

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