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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 584 · 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. 1.57 + 19 =
  2. 2.334 + 99 =
  3. 3.26 + 9 =
  4. 4.80 − 9 =
  5. 5.37 − 19 =
  6. 6.73 + 9 =
  7. 7.76 − 19 =
  8. 8.41 + 9 =
  9. 9.710 + 99 =
  10. 10.35 + 29 =
  11. 11.68 + 9 =
  12. 12.38 − 29 =
  13. 13.33 − 29 =
  14. 14.32 − 19 =
  15. 15.398 − 99 =
  16. 16.22 + 29 =
  17. 17.426 − 99 =
  18. 18.558 − 99 =
  19. 19.733 + 99 =
  20. 20.66 + 29 =
  21. 21.631 + 99 =
  22. 22.68 − 9 =
  23. 23.59 − 29 =
  24. 24.92 − 29 =
  25. 25.661 + 99 =
  26. 26.25 − 19 =
  27. 27.36 + 19 =
  28. 28.33 + 29 =
  29. 29.39 − 29 =
  30. 30.12 + 9 =
  31. 31.32 + 9 =
  32. 32.49 − 9 =
  33. 33.69 + 9 =
  34. 34.60 + 29 =
  35. 35.158 − 99 =
  36. 36.71 + 29 =
  37. 37.49 − 29 =
  38. 38.65 − 29 =
  39. 39.15 − 9 =
  40. 40.19 + 19 =

Answer key

  1. 76
  2. 433
  3. 35
  4. 71
  5. 18
  6. 82
  7. 57
  8. 50
  9. 809
  10. 64
  11. 77
  12. 9
  13. 4
  14. 13
  15. 299
  16. 51
  17. 327
  18. 459
  19. 832
  20. 95
  21. 730
  22. 59
  23. 30
  24. 63
  25. 760
  26. 6
  27. 55
  28. 62
  29. 10
  30. 21
  31. 41
  32. 40
  33. 78
  34. 89
  35. 59
  36. 100
  37. 20
  38. 36
  39. 6
  40. 38

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