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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 783 · 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. 1.361 + 99 =
  2. 2.497 − 99 =
  3. 3.56 + 29 =
  4. 4.688 + 99 =
  5. 5.69 + 9 =
  6. 6.348 − 99 =
  7. 7.67 + 9 =
  8. 8.59 − 9 =
  9. 9.296 − 99 =
  10. 10.62 + 9 =
  11. 11.733 + 99 =
  12. 12.16 + 9 =
  13. 13.724 + 99 =
  14. 14.25 + 9 =
  15. 15.66 − 29 =
  16. 16.67 − 19 =
  17. 17.56 + 19 =
  18. 18.52 + 19 =
  19. 19.872 − 99 =
  20. 20.63 + 19 =
  21. 21.61 − 9 =
  22. 22.85 − 19 =
  23. 23.35 + 19 =
  24. 24.27 + 19 =
  25. 25.75 − 29 =
  26. 26.54 + 9 =
  27. 27.349 + 99 =
  28. 28.12 + 9 =
  29. 29.178 − 99 =
  30. 30.17 + 19 =
  31. 31.23 + 19 =
  32. 32.43 − 19 =
  33. 33.71 + 19 =
  34. 34.80 − 29 =
  35. 35.759 + 99 =
  36. 36.64 + 19 =
  37. 37.29 − 19 =
  38. 38.233 + 99 =
  39. 39.71 + 9 =
  40. 40.66 + 29 =

Answer key

  1. 460
  2. 398
  3. 85
  4. 787
  5. 78
  6. 249
  7. 76
  8. 50
  9. 197
  10. 71
  11. 832
  12. 25
  13. 823
  14. 34
  15. 37
  16. 48
  17. 75
  18. 71
  19. 773
  20. 82
  21. 52
  22. 66
  23. 54
  24. 46
  25. 46
  26. 63
  27. 448
  28. 21
  29. 79
  30. 36
  31. 42
  32. 24
  33. 90
  34. 51
  35. 858
  36. 83
  37. 10
  38. 332
  39. 80
  40. 95

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