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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 751 · 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. 1.586 + 99 =
  2. 2.78 − 19 =
  3. 3.30 − 9 =
  4. 4.668 − 99 =
  5. 5.481 + 99 =
  6. 6.48 + 19 =
  7. 7.83 − 9 =
  8. 8.28 + 9 =
  9. 9.92 − 19 =
  10. 10.43 + 9 =
  11. 11.75 − 19 =
  12. 12.73 + 9 =
  13. 13.60 + 19 =
  14. 14.67 − 9 =
  15. 15.29 − 19 =
  16. 16.74 + 9 =
  17. 17.483 + 99 =
  18. 18.29 + 29 =
  19. 19.78 + 9 =
  20. 20.50 − 19 =
  21. 21.31 − 19 =
  22. 22.89 − 9 =
  23. 23.212 − 99 =
  24. 24.61 − 9 =
  25. 25.592 − 99 =
  26. 26.60 + 29 =
  27. 27.16 + 29 =
  28. 28.59 + 29 =
  29. 29.409 − 99 =
  30. 30.40 + 19 =
  31. 31.13 − 9 =
  32. 32.61 + 9 =
  33. 33.45 + 29 =
  34. 34.32 + 9 =
  35. 35.67 + 29 =
  36. 36.213 − 99 =
  37. 37.49 − 29 =
  38. 38.30 + 19 =
  39. 39.65 + 29 =
  40. 40.50 + 9 =

Answer key

  1. 685
  2. 59
  3. 21
  4. 569
  5. 580
  6. 67
  7. 74
  8. 37
  9. 73
  10. 52
  11. 56
  12. 82
  13. 79
  14. 58
  15. 10
  16. 83
  17. 582
  18. 58
  19. 87
  20. 31
  21. 12
  22. 80
  23. 113
  24. 52
  25. 493
  26. 89
  27. 45
  28. 88
  29. 310
  30. 59
  31. 4
  32. 70
  33. 74
  34. 41
  35. 96
  36. 114
  37. 20
  38. 49
  39. 94
  40. 59

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