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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 148 · 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. 1.21 + 19 =
  2. 2.58 + 19 =
  3. 3.34 − 9 =
  4. 4.23 + 29 =
  5. 5.337 − 99 =
  6. 6.680 − 99 =
  7. 7.805 − 99 =
  8. 8.85 − 9 =
  9. 9.38 + 9 =
  10. 10.57 + 19 =
  11. 11.241 − 99 =
  12. 12.469 + 99 =
  13. 13.89 − 29 =
  14. 14.61 − 9 =
  15. 15.82 − 29 =
  16. 16.51 + 9 =
  17. 17.28 − 9 =
  18. 18.37 − 9 =
  19. 19.58 + 29 =
  20. 20.77 + 29 =
  21. 21.19 + 9 =
  22. 22.13 + 29 =
  23. 23.824 − 99 =
  24. 24.91 − 19 =
  25. 25.50 + 29 =
  26. 26.384 − 99 =
  27. 27.28 + 9 =
  28. 28.77 − 19 =
  29. 29.699 − 99 =
  30. 30.12 + 9 =
  31. 31.72 + 29 =
  32. 32.168 + 99 =
  33. 33.349 + 99 =
  34. 34.26 − 19 =
  35. 35.113 + 99 =
  36. 36.25 + 9 =
  37. 37.27 − 9 =
  38. 38.62 + 29 =
  39. 39.54 − 29 =
  40. 40.779 − 99 =

Answer key

  1. 40
  2. 77
  3. 25
  4. 52
  5. 238
  6. 581
  7. 706
  8. 76
  9. 47
  10. 76
  11. 142
  12. 568
  13. 60
  14. 52
  15. 53
  16. 60
  17. 19
  18. 28
  19. 87
  20. 106
  21. 28
  22. 42
  23. 725
  24. 72
  25. 79
  26. 285
  27. 37
  28. 58
  29. 600
  30. 21
  31. 101
  32. 267
  33. 448
  34. 7
  35. 212
  36. 34
  37. 18
  38. 91
  39. 25
  40. 680

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