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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 406 · 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. 1.93 − 19 =
  2. 2.622 + 99 =
  3. 3.82 − 19 =
  4. 4.65 + 29 =
  5. 5.42 + 9 =
  6. 6.58 − 29 =
  7. 7.276 − 99 =
  8. 8.625 + 99 =
  9. 9.26 + 29 =
  10. 10.57 + 19 =
  11. 11.17 + 9 =
  12. 12.24 − 19 =
  13. 13.601 + 99 =
  14. 14.271 − 99 =
  15. 15.52 + 9 =
  16. 16.83 − 29 =
  17. 17.773 − 99 =
  18. 18.173 + 99 =
  19. 19.66 + 9 =
  20. 20.23 + 29 =
  21. 21.65 + 19 =
  22. 22.269 + 99 =
  23. 23.33 + 29 =
  24. 24.53 + 29 =
  25. 25.14 − 9 =
  26. 26.23 + 9 =
  27. 27.80 − 9 =
  28. 28.48 + 19 =
  29. 29.45 + 9 =
  30. 30.18 + 19 =
  31. 31.478 + 99 =
  32. 32.65 − 9 =
  33. 33.70 − 9 =
  34. 34.37 + 29 =
  35. 35.104 − 29 =
  36. 36.28 − 19 =
  37. 37.84 − 29 =
  38. 38.71 + 29 =
  39. 39.97 − 19 =
  40. 40.19 + 19 =

Answer key

  1. 74
  2. 721
  3. 63
  4. 94
  5. 51
  6. 29
  7. 177
  8. 724
  9. 55
  10. 76
  11. 26
  12. 5
  13. 700
  14. 172
  15. 61
  16. 54
  17. 674
  18. 272
  19. 75
  20. 52
  21. 84
  22. 368
  23. 62
  24. 82
  25. 5
  26. 32
  27. 71
  28. 67
  29. 54
  30. 37
  31. 577
  32. 56
  33. 61
  34. 66
  35. 75
  36. 9
  37. 55
  38. 100
  39. 78
  40. 38

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