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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 437 · 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. 1.51 − 29 =
  2. 2.31 + 19 =
  3. 3.12 − 9 =
  4. 4.15 + 29 =
  5. 5.30 − 19 =
  6. 6.75 + 9 =
  7. 7.728 + 99 =
  8. 8.36 − 9 =
  9. 9.80 − 19 =
  10. 10.91 − 29 =
  11. 11.57 + 19 =
  12. 12.64 + 19 =
  13. 13.37 + 9 =
  14. 14.21 + 9 =
  15. 15.68 + 9 =
  16. 16.659 + 99 =
  17. 17.63 + 9 =
  18. 18.71 + 29 =
  19. 19.23 + 29 =
  20. 20.73 + 9 =
  21. 21.28 + 29 =
  22. 22.219 + 99 =
  23. 23.67 − 29 =
  24. 24.26 − 19 =
  25. 25.28 + 19 =
  26. 26.32 + 9 =
  27. 27.27 + 29 =
  28. 28.366 + 99 =
  29. 29.98 − 19 =
  30. 30.86 − 29 =
  31. 31.259 − 99 =
  32. 32.296 + 99 =
  33. 33.88 − 9 =
  34. 34.73 − 29 =
  35. 35.61 + 19 =
  36. 36.350 + 99 =
  37. 37.25 + 19 =
  38. 38.333 + 99 =
  39. 39.78 − 19 =
  40. 40.51 + 29 =

Answer key

  1. 22
  2. 50
  3. 3
  4. 44
  5. 11
  6. 84
  7. 827
  8. 27
  9. 61
  10. 62
  11. 76
  12. 83
  13. 46
  14. 30
  15. 77
  16. 758
  17. 72
  18. 100
  19. 52
  20. 82
  21. 57
  22. 318
  23. 38
  24. 7
  25. 47
  26. 41
  27. 56
  28. 465
  29. 79
  30. 57
  31. 160
  32. 395
  33. 79
  34. 44
  35. 80
  36. 449
  37. 44
  38. 432
  39. 59
  40. 80

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