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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 259 · 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. 1.25 + 19 =
  2. 2.552 − 99 =
  3. 3.315 + 99 =
  4. 4.26 + 19 =
  5. 5.14 + 9 =
  6. 6.89 − 19 =
  7. 7.74 + 9 =
  8. 8.795 + 99 =
  9. 9.254 + 99 =
  10. 10.56 + 9 =
  11. 11.538 − 99 =
  12. 12.59 − 9 =
  13. 13.27 + 29 =
  14. 14.752 + 99 =
  15. 15.762 + 99 =
  16. 16.39 + 9 =
  17. 17.19 + 19 =
  18. 18.595 + 99 =
  19. 19.67 + 29 =
  20. 20.15 + 9 =
  21. 21.70 + 9 =
  22. 22.69 − 19 =
  23. 23.868 − 99 =
  24. 24.86 − 29 =
  25. 25.61 + 19 =
  26. 26.44 + 19 =
  27. 27.383 + 99 =
  28. 28.430 + 99 =
  29. 29.24 − 9 =
  30. 30.26 + 9 =
  31. 31.56 − 9 =
  32. 32.67 − 9 =
  33. 33.88 − 29 =
  34. 34.35 + 19 =
  35. 35.85 − 9 =
  36. 36.67 − 29 =
  37. 37.80 − 29 =
  38. 38.58 + 29 =
  39. 39.19 + 9 =
  40. 40.517 − 99 =

Answer key

  1. 44
  2. 453
  3. 414
  4. 45
  5. 23
  6. 70
  7. 83
  8. 894
  9. 353
  10. 65
  11. 439
  12. 50
  13. 56
  14. 851
  15. 861
  16. 48
  17. 38
  18. 694
  19. 96
  20. 24
  21. 79
  22. 50
  23. 769
  24. 57
  25. 80
  26. 63
  27. 482
  28. 529
  29. 15
  30. 35
  31. 47
  32. 58
  33. 59
  34. 54
  35. 76
  36. 38
  37. 51
  38. 87
  39. 28
  40. 418

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