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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 390 · 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. 1.348 − 99 =
  2. 2.85 − 9 =
  3. 3.41 + 19 =
  4. 4.25 − 9 =
  5. 5.52 + 9 =
  6. 6.36 + 9 =
  7. 7.24 + 9 =
  8. 8.60 − 29 =
  9. 9.64 − 29 =
  10. 10.83 − 9 =
  11. 11.91 − 29 =
  12. 12.12 + 29 =
  13. 13.39 + 9 =
  14. 14.77 − 9 =
  15. 15.82 − 19 =
  16. 16.411 + 99 =
  17. 17.62 − 19 =
  18. 18.48 + 9 =
  19. 19.18 + 19 =
  20. 20.857 − 99 =
  21. 21.14 + 9 =
  22. 22.83 − 19 =
  23. 23.15 + 9 =
  24. 24.849 − 99 =
  25. 25.68 + 29 =
  26. 26.68 − 19 =
  27. 27.72 − 9 =
  28. 28.64 + 29 =
  29. 29.17 + 9 =
  30. 30.14 + 19 =
  31. 31.37 + 19 =
  32. 32.84 − 19 =
  33. 33.68 + 19 =
  34. 34.206 + 99 =
  35. 35.74 − 29 =
  36. 36.80 + 19 =
  37. 37.42 − 9 =
  38. 38.568 − 99 =
  39. 39.507 + 99 =
  40. 40.75 − 29 =

Answer key

  1. 249
  2. 76
  3. 60
  4. 16
  5. 61
  6. 45
  7. 33
  8. 31
  9. 35
  10. 74
  11. 62
  12. 41
  13. 48
  14. 68
  15. 63
  16. 510
  17. 43
  18. 57
  19. 37
  20. 758
  21. 23
  22. 64
  23. 24
  24. 750
  25. 97
  26. 49
  27. 63
  28. 93
  29. 26
  30. 33
  31. 56
  32. 65
  33. 87
  34. 305
  35. 45
  36. 99
  37. 33
  38. 469
  39. 606
  40. 46

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