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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 535 · 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. 1.16 − 9 =
  2. 2.39 − 29 =
  3. 3.78 + 19 =
  4. 4.25 − 19 =
  5. 5.858 − 99 =
  6. 6.45 − 29 =
  7. 7.75 + 19 =
  8. 8.88 − 29 =
  9. 9.77 + 9 =
  10. 10.40 + 19 =
  11. 11.66 − 29 =
  12. 12.670 − 99 =
  13. 13.32 + 19 =
  14. 14.21 − 9 =
  15. 15.620 − 99 =
  16. 16.82 − 19 =
  17. 17.56 − 9 =
  18. 18.395 + 99 =
  19. 19.16 + 19 =
  20. 20.346 + 99 =
  21. 21.46 − 9 =
  22. 22.79 + 29 =
  23. 23.227 + 99 =
  24. 24.47 − 29 =
  25. 25.196 − 99 =
  26. 26.44 + 19 =
  27. 27.52 + 19 =
  28. 28.23 + 29 =
  29. 29.764 − 99 =
  30. 30.809 − 99 =
  31. 31.81 − 9 =
  32. 32.69 − 9 =
  33. 33.59 + 19 =
  34. 34.84 − 29 =
  35. 35.14 − 9 =
  36. 36.63 + 19 =
  37. 37.80 + 19 =
  38. 38.33 + 29 =
  39. 39.340 − 99 =
  40. 40.384 − 99 =

Answer key

  1. 7
  2. 10
  3. 97
  4. 6
  5. 759
  6. 16
  7. 94
  8. 59
  9. 86
  10. 59
  11. 37
  12. 571
  13. 51
  14. 12
  15. 521
  16. 63
  17. 47
  18. 494
  19. 35
  20. 445
  21. 37
  22. 108
  23. 326
  24. 18
  25. 97
  26. 63
  27. 71
  28. 52
  29. 665
  30. 710
  31. 72
  32. 60
  33. 78
  34. 55
  35. 5
  36. 82
  37. 99
  38. 62
  39. 241
  40. 285

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