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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 95 · 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. 1.65 + 29 =
  2. 2.29 + 19 =
  3. 3.52 − 29 =
  4. 4.71 + 19 =
  5. 5.338 + 99 =
  6. 6.56 − 29 =
  7. 7.292 + 99 =
  8. 8.42 + 19 =
  9. 9.724 + 99 =
  10. 10.76 + 29 =
  11. 11.49 − 9 =
  12. 12.242 − 99 =
  13. 13.18 + 9 =
  14. 14.639 − 99 =
  15. 15.47 − 29 =
  16. 16.41 + 9 =
  17. 17.454 − 99 =
  18. 18.13 + 9 =
  19. 19.91 − 29 =
  20. 20.58 − 9 =
  21. 21.59 + 19 =
  22. 22.50 − 9 =
  23. 23.45 + 9 =
  24. 24.74 + 9 =
  25. 25.77 + 29 =
  26. 26.23 + 29 =
  27. 27.51 − 9 =
  28. 28.649 + 99 =
  29. 29.62 + 9 =
  30. 30.60 − 29 =
  31. 31.36 − 9 =
  32. 32.100 − 29 =
  33. 33.21 + 9 =
  34. 34.81 − 9 =
  35. 35.42 − 29 =
  36. 36.206 − 99 =
  37. 37.49 + 29 =
  38. 38.44 + 29 =
  39. 39.847 − 99 =
  40. 40.56 + 9 =

Answer key

  1. 94
  2. 48
  3. 23
  4. 90
  5. 437
  6. 27
  7. 391
  8. 61
  9. 823
  10. 105
  11. 40
  12. 143
  13. 27
  14. 540
  15. 18
  16. 50
  17. 355
  18. 22
  19. 62
  20. 49
  21. 78
  22. 41
  23. 54
  24. 83
  25. 106
  26. 52
  27. 42
  28. 748
  29. 71
  30. 31
  31. 27
  32. 71
  33. 30
  34. 72
  35. 13
  36. 107
  37. 78
  38. 73
  39. 748
  40. 65

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