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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 701 · 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. 1.25 + 9 =
  2. 2.45 − 29 =
  3. 3.79 + 9 =
  4. 4.67 + 29 =
  5. 5.207 + 99 =
  6. 6.74 + 9 =
  7. 7.43 + 19 =
  8. 8.23 + 9 =
  9. 9.23 + 29 =
  10. 10.249 + 99 =
  11. 11.46 + 19 =
  12. 12.53 − 29 =
  13. 13.57 + 29 =
  14. 14.94 − 29 =
  15. 15.17 + 19 =
  16. 16.63 + 9 =
  17. 17.96 − 19 =
  18. 18.78 + 29 =
  19. 19.61 − 29 =
  20. 20.55 + 29 =
  21. 21.25 − 9 =
  22. 22.29 + 9 =
  23. 23.46 − 29 =
  24. 24.41 + 19 =
  25. 25.34 − 19 =
  26. 26.750 − 99 =
  27. 27.865 − 99 =
  28. 28.14 − 9 =
  29. 29.44 + 9 =
  30. 30.33 + 29 =
  31. 31.74 + 19 =
  32. 32.68 − 9 =
  33. 33.571 + 99 =
  34. 34.56 + 9 =
  35. 35.548 − 99 =
  36. 36.50 + 19 =
  37. 37.262 − 99 =
  38. 38.88 − 9 =
  39. 39.45 − 19 =
  40. 40.17 − 9 =

Answer key

  1. 34
  2. 16
  3. 88
  4. 96
  5. 306
  6. 83
  7. 62
  8. 32
  9. 52
  10. 348
  11. 65
  12. 24
  13. 86
  14. 65
  15. 36
  16. 72
  17. 77
  18. 107
  19. 32
  20. 84
  21. 16
  22. 38
  23. 17
  24. 60
  25. 15
  26. 651
  27. 766
  28. 5
  29. 53
  30. 62
  31. 93
  32. 59
  33. 670
  34. 65
  35. 449
  36. 69
  37. 163
  38. 79
  39. 26
  40. 8

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