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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 22 · 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. 1.89 − 19 =
  2. 2.36 − 29 =
  3. 3.47 + 29 =
  4. 4.22 + 29 =
  5. 5.552 + 99 =
  6. 6.339 + 99 =
  7. 7.71 − 29 =
  8. 8.90 − 29 =
  9. 9.24 − 19 =
  10. 10.64 + 29 =
  11. 11.67 − 29 =
  12. 12.466 − 99 =
  13. 13.298 + 99 =
  14. 14.84 − 29 =
  15. 15.68 + 9 =
  16. 16.478 + 99 =
  17. 17.39 − 29 =
  18. 18.95 − 29 =
  19. 19.185 − 99 =
  20. 20.61 + 9 =
  21. 21.82 − 29 =
  22. 22.55 − 29 =
  23. 23.86 − 29 =
  24. 24.755 − 99 =
  25. 25.76 + 9 =
  26. 26.74 + 29 =
  27. 27.49 − 9 =
  28. 28.45 + 29 =
  29. 29.628 − 99 =
  30. 30.40 − 9 =
  31. 31.67 − 19 =
  32. 32.117 + 99 =
  33. 33.48 + 29 =
  34. 34.67 + 9 =
  35. 35.330 + 99 =
  36. 36.844 − 99 =
  37. 37.64 − 19 =
  38. 38.48 + 9 =
  39. 39.31 + 9 =
  40. 40.457 + 99 =

Answer key

  1. 70
  2. 7
  3. 76
  4. 51
  5. 651
  6. 438
  7. 42
  8. 61
  9. 5
  10. 93
  11. 38
  12. 367
  13. 397
  14. 55
  15. 77
  16. 577
  17. 10
  18. 66
  19. 86
  20. 70
  21. 53
  22. 26
  23. 57
  24. 656
  25. 85
  26. 103
  27. 40
  28. 74
  29. 529
  30. 31
  31. 48
  32. 216
  33. 77
  34. 76
  35. 429
  36. 745
  37. 45
  38. 57
  39. 40
  40. 556

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