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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 511 · 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. 1.72 + 9 =
  2. 2.40 + 29 =
  3. 3.15 − 9 =
  4. 4.22 + 29 =
  5. 5.20 + 9 =
  6. 6.27 + 9 =
  7. 7.200 − 99 =
  8. 8.79 + 29 =
  9. 9.87 − 29 =
  10. 10.607 − 99 =
  11. 11.60 + 29 =
  12. 12.69 + 19 =
  13. 13.77 − 19 =
  14. 14.70 + 19 =
  15. 15.46 − 9 =
  16. 16.50 − 9 =
  17. 17.65 + 29 =
  18. 18.48 + 29 =
  19. 19.164 − 99 =
  20. 20.19 + 19 =
  21. 21.86 − 9 =
  22. 22.49 + 9 =
  23. 23.42 − 29 =
  24. 24.29 − 9 =
  25. 25.38 − 29 =
  26. 26.200 + 99 =
  27. 27.95 − 19 =
  28. 28.134 + 99 =
  29. 29.39 + 9 =
  30. 30.192 − 99 =
  31. 31.88 − 9 =
  32. 32.48 − 19 =
  33. 33.79 − 19 =
  34. 34.22 + 19 =
  35. 35.24 + 29 =
  36. 36.50 − 19 =
  37. 37.30 + 29 =
  38. 38.17 + 19 =
  39. 39.282 + 99 =
  40. 40.731 + 99 =

Answer key

  1. 81
  2. 69
  3. 6
  4. 51
  5. 29
  6. 36
  7. 101
  8. 108
  9. 58
  10. 508
  11. 89
  12. 88
  13. 58
  14. 89
  15. 37
  16. 41
  17. 94
  18. 77
  19. 65
  20. 38
  21. 77
  22. 58
  23. 13
  24. 20
  25. 9
  26. 299
  27. 76
  28. 233
  29. 48
  30. 93
  31. 79
  32. 29
  33. 60
  34. 41
  35. 53
  36. 31
  37. 59
  38. 36
  39. 381
  40. 830

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