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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 643 · 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. 1.53 − 9 =
  2. 2.21 + 29 =
  3. 3.55 + 19 =
  4. 4.49 + 19 =
  5. 5.79 − 9 =
  6. 6.76 − 29 =
  7. 7.53 − 19 =
  8. 8.39 + 29 =
  9. 9.21 + 19 =
  10. 10.36 − 9 =
  11. 11.253 − 99 =
  12. 12.425 + 99 =
  13. 13.72 − 9 =
  14. 14.33 − 9 =
  15. 15.411 + 99 =
  16. 16.513 − 99 =
  17. 17.58 − 9 =
  18. 18.77 + 9 =
  19. 19.48 + 19 =
  20. 20.357 + 99 =
  21. 21.68 − 29 =
  22. 22.16 + 9 =
  23. 23.56 + 9 =
  24. 24.73 + 9 =
  25. 25.310 + 99 =
  26. 26.60 − 29 =
  27. 27.33 − 19 =
  28. 28.19 + 9 =
  29. 29.397 − 99 =
  30. 30.17 + 9 =
  31. 31.69 + 9 =
  32. 32.12 + 19 =
  33. 33.475 + 99 =
  34. 34.39 − 9 =
  35. 35.60 − 9 =
  36. 36.291 − 99 =
  37. 37.740 + 99 =
  38. 38.765 + 99 =
  39. 39.54 + 9 =
  40. 40.790 + 99 =

Answer key

  1. 44
  2. 50
  3. 74
  4. 68
  5. 70
  6. 47
  7. 34
  8. 68
  9. 40
  10. 27
  11. 154
  12. 524
  13. 63
  14. 24
  15. 510
  16. 414
  17. 49
  18. 86
  19. 67
  20. 456
  21. 39
  22. 25
  23. 65
  24. 82
  25. 409
  26. 31
  27. 14
  28. 28
  29. 298
  30. 26
  31. 78
  32. 31
  33. 574
  34. 30
  35. 51
  36. 192
  37. 839
  38. 864
  39. 63
  40. 889

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