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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 653 · 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. 1.28 + 19 =
  2. 2.27 + 9 =
  3. 3.80 − 29 =
  4. 4.57 + 29 =
  5. 5.53 + 29 =
  6. 6.73 − 29 =
  7. 7.88 − 19 =
  8. 8.827 − 99 =
  9. 9.721 + 99 =
  10. 10.18 + 9 =
  11. 11.58 − 19 =
  12. 12.267 + 99 =
  13. 13.68 − 29 =
  14. 14.283 − 99 =
  15. 15.233 + 99 =
  16. 16.690 − 99 =
  17. 17.54 + 9 =
  18. 18.59 − 29 =
  19. 19.69 − 9 =
  20. 20.21 − 9 =
  21. 21.75 − 9 =
  22. 22.59 + 9 =
  23. 23.33 − 19 =
  24. 24.47 + 9 =
  25. 25.39 − 19 =
  26. 26.299 + 99 =
  27. 27.277 − 99 =
  28. 28.27 + 29 =
  29. 29.65 + 19 =
  30. 30.38 − 29 =
  31. 31.17 + 9 =
  32. 32.522 − 99 =
  33. 33.30 + 19 =
  34. 34.49 + 9 =
  35. 35.34 − 9 =
  36. 36.539 + 99 =
  37. 37.23 + 19 =
  38. 38.33 + 9 =
  39. 39.789 + 99 =
  40. 40.15 + 29 =

Answer key

  1. 47
  2. 36
  3. 51
  4. 86
  5. 82
  6. 44
  7. 69
  8. 728
  9. 820
  10. 27
  11. 39
  12. 366
  13. 39
  14. 184
  15. 332
  16. 591
  17. 63
  18. 30
  19. 60
  20. 12
  21. 66
  22. 68
  23. 14
  24. 56
  25. 20
  26. 398
  27. 178
  28. 56
  29. 84
  30. 9
  31. 26
  32. 423
  33. 49
  34. 58
  35. 25
  36. 638
  37. 42
  38. 42
  39. 888
  40. 44

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