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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 24 · 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. 1.33 − 19 =
  2. 2.13 + 9 =
  3. 3.93 − 29 =
  4. 4.361 + 99 =
  5. 5.51 − 29 =
  6. 6.306 − 99 =
  7. 7.677 + 99 =
  8. 8.68 + 19 =
  9. 9.62 − 29 =
  10. 10.41 + 19 =
  11. 11.44 − 19 =
  12. 12.57 + 29 =
  13. 13.14 + 9 =
  14. 14.36 + 19 =
  15. 15.83 − 29 =
  16. 16.48 − 9 =
  17. 17.14 + 29 =
  18. 18.416 − 99 =
  19. 19.56 − 19 =
  20. 20.175 + 99 =
  21. 21.20 + 19 =
  22. 22.41 − 19 =
  23. 23.52 − 19 =
  24. 24.46 − 29 =
  25. 25.59 − 9 =
  26. 26.58 − 29 =
  27. 27.12 − 9 =
  28. 28.99 − 19 =
  29. 29.33 − 9 =
  30. 30.767 − 99 =
  31. 31.68 + 9 =
  32. 32.40 + 9 =
  33. 33.467 + 99 =
  34. 34.58 + 9 =
  35. 35.52 + 29 =
  36. 36.49 + 29 =
  37. 37.85 − 9 =
  38. 38.26 + 9 =
  39. 39.400 + 99 =
  40. 40.766 + 99 =

Answer key

  1. 14
  2. 22
  3. 64
  4. 460
  5. 22
  6. 207
  7. 776
  8. 87
  9. 33
  10. 60
  11. 25
  12. 86
  13. 23
  14. 55
  15. 54
  16. 39
  17. 43
  18. 317
  19. 37
  20. 274
  21. 39
  22. 22
  23. 33
  24. 17
  25. 50
  26. 29
  27. 3
  28. 80
  29. 24
  30. 668
  31. 77
  32. 49
  33. 566
  34. 67
  35. 81
  36. 78
  37. 76
  38. 35
  39. 499
  40. 865

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