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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 717 · 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. 1.91 − 29 =
  2. 2.26 − 9 =
  3. 3.65 + 29 =
  4. 4.798 + 99 =
  5. 5.58 + 19 =
  6. 6.32 + 19 =
  7. 7.64 − 29 =
  8. 8.750 − 99 =
  9. 9.44 − 19 =
  10. 10.528 + 99 =
  11. 11.886 − 99 =
  12. 12.62 + 29 =
  13. 13.71 − 29 =
  14. 14.25 + 19 =
  15. 15.70 + 29 =
  16. 16.342 − 99 =
  17. 17.29 + 9 =
  18. 18.76 − 9 =
  19. 19.24 + 9 =
  20. 20.37 + 9 =
  21. 21.101 − 29 =
  22. 22.82 − 9 =
  23. 23.551 + 99 =
  24. 24.72 + 29 =
  25. 25.61 + 29 =
  26. 26.15 + 9 =
  27. 27.59 + 29 =
  28. 28.31 + 29 =
  29. 29.32 + 9 =
  30. 30.725 − 99 =
  31. 31.78 − 19 =
  32. 32.51 + 9 =
  33. 33.705 + 99 =
  34. 34.19 − 9 =
  35. 35.17 + 19 =
  36. 36.88 − 29 =
  37. 37.40 − 29 =
  38. 38.665 + 99 =
  39. 39.47 + 19 =
  40. 40.398 − 99 =

Answer key

  1. 62
  2. 17
  3. 94
  4. 897
  5. 77
  6. 51
  7. 35
  8. 651
  9. 25
  10. 627
  11. 787
  12. 91
  13. 42
  14. 44
  15. 99
  16. 243
  17. 38
  18. 67
  19. 33
  20. 46
  21. 72
  22. 73
  23. 650
  24. 101
  25. 90
  26. 24
  27. 88
  28. 60
  29. 41
  30. 626
  31. 59
  32. 60
  33. 804
  34. 10
  35. 36
  36. 59
  37. 11
  38. 764
  39. 66
  40. 299

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