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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 202 · 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. 1.794 − 99 =
  2. 2.21 + 29 =
  3. 3.87 − 29 =
  4. 4.64 − 9 =
  5. 5.80 − 19 =
  6. 6.15 − 9 =
  7. 7.26 − 9 =
  8. 8.54 − 19 =
  9. 9.33 − 19 =
  10. 10.82 − 9 =
  11. 11.65 − 19 =
  12. 12.62 + 9 =
  13. 13.362 − 99 =
  14. 14.769 + 99 =
  15. 15.79 − 9 =
  16. 16.27 + 29 =
  17. 17.19 + 29 =
  18. 18.80 + 9 =
  19. 19.16 + 29 =
  20. 20.119 + 99 =
  21. 21.55 + 9 =
  22. 22.66 + 9 =
  23. 23.35 − 19 =
  24. 24.50 + 9 =
  25. 25.45 − 19 =
  26. 26.502 + 99 =
  27. 27.138 + 99 =
  28. 28.24 + 29 =
  29. 29.70 − 29 =
  30. 30.56 − 9 =
  31. 31.18 + 29 =
  32. 32.42 − 19 =
  33. 33.71 + 19 =
  34. 34.511 − 99 =
  35. 35.53 + 29 =
  36. 36.42 + 19 =
  37. 37.21 − 9 =
  38. 38.48 − 9 =
  39. 39.46 − 29 =
  40. 40.72 + 9 =

Answer key

  1. 695
  2. 50
  3. 58
  4. 55
  5. 61
  6. 6
  7. 17
  8. 35
  9. 14
  10. 73
  11. 46
  12. 71
  13. 263
  14. 868
  15. 70
  16. 56
  17. 48
  18. 89
  19. 45
  20. 218
  21. 64
  22. 75
  23. 16
  24. 59
  25. 26
  26. 601
  27. 237
  28. 53
  29. 41
  30. 47
  31. 47
  32. 23
  33. 90
  34. 412
  35. 82
  36. 61
  37. 12
  38. 39
  39. 17
  40. 81

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