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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 479 · 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. 1.41 − 19 =
  2. 2.626 + 99 =
  3. 3.22 + 29 =
  4. 4.58 + 29 =
  5. 5.14 + 9 =
  6. 6.32 + 29 =
  7. 7.19 + 9 =
  8. 8.39 − 9 =
  9. 9.81 − 29 =
  10. 10.288 − 99 =
  11. 11.69 + 19 =
  12. 12.231 + 99 =
  13. 13.16 + 29 =
  14. 14.20 + 9 =
  15. 15.55 − 9 =
  16. 16.71 − 29 =
  17. 17.73 + 29 =
  18. 18.178 + 99 =
  19. 19.452 + 99 =
  20. 20.31 + 19 =
  21. 21.31 + 29 =
  22. 22.21 + 19 =
  23. 23.38 + 9 =
  24. 24.40 − 9 =
  25. 25.615 − 99 =
  26. 26.18 − 9 =
  27. 27.56 + 9 =
  28. 28.23 − 9 =
  29. 29.32 − 29 =
  30. 30.54 + 9 =
  31. 31.617 − 99 =
  32. 32.68 − 29 =
  33. 33.42 + 19 =
  34. 34.55 − 29 =
  35. 35.71 + 19 =
  36. 36.70 − 9 =
  37. 37.416 − 99 =
  38. 38.38 − 19 =
  39. 39.20 + 19 =
  40. 40.45 − 9 =

Answer key

  1. 22
  2. 725
  3. 51
  4. 87
  5. 23
  6. 61
  7. 28
  8. 30
  9. 52
  10. 189
  11. 88
  12. 330
  13. 45
  14. 29
  15. 46
  16. 42
  17. 102
  18. 277
  19. 551
  20. 50
  21. 60
  22. 40
  23. 47
  24. 31
  25. 516
  26. 9
  27. 65
  28. 14
  29. 3
  30. 63
  31. 518
  32. 39
  33. 61
  34. 26
  35. 90
  36. 61
  37. 317
  38. 19
  39. 39
  40. 36

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