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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 581 · 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. 1.47 + 19 =
  2. 2.56 − 29 =
  3. 3.848 − 99 =
  4. 4.100 − 29 =
  5. 5.55 − 9 =
  6. 6.30 + 9 =
  7. 7.46 − 29 =
  8. 8.781 − 99 =
  9. 9.53 − 29 =
  10. 10.71 − 19 =
  11. 11.78 − 9 =
  12. 12.89 − 29 =
  13. 13.223 − 99 =
  14. 14.27 + 9 =
  15. 15.17 + 29 =
  16. 16.17 − 9 =
  17. 17.60 + 29 =
  18. 18.24 − 19 =
  19. 19.15 + 9 =
  20. 20.79 + 9 =
  21. 21.677 − 99 =
  22. 22.336 − 99 =
  23. 23.50 − 29 =
  24. 24.77 + 29 =
  25. 25.24 + 9 =
  26. 26.732 + 99 =
  27. 27.41 − 9 =
  28. 28.381 + 99 =
  29. 29.87 − 29 =
  30. 30.48 − 29 =
  31. 31.107 − 29 =
  32. 32.693 − 99 =
  33. 33.54 − 9 =
  34. 34.70 − 9 =
  35. 35.31 + 19 =
  36. 36.611 − 99 =
  37. 37.29 + 29 =
  38. 38.211 + 99 =
  39. 39.81 − 9 =
  40. 40.80 − 9 =

Answer key

  1. 66
  2. 27
  3. 749
  4. 71
  5. 46
  6. 39
  7. 17
  8. 682
  9. 24
  10. 52
  11. 69
  12. 60
  13. 124
  14. 36
  15. 46
  16. 8
  17. 89
  18. 5
  19. 24
  20. 88
  21. 578
  22. 237
  23. 21
  24. 106
  25. 33
  26. 831
  27. 32
  28. 480
  29. 58
  30. 19
  31. 78
  32. 594
  33. 45
  34. 61
  35. 50
  36. 512
  37. 58
  38. 310
  39. 72
  40. 71

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