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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 893 · 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. 1.42 − 29 =
  2. 2.747 + 99 =
  3. 3.33 − 9 =
  4. 4.502 + 99 =
  5. 5.43 − 29 =
  6. 6.35 + 19 =
  7. 7.77 + 19 =
  8. 8.73 + 19 =
  9. 9.30 + 19 =
  10. 10.13 − 9 =
  11. 11.788 + 99 =
  12. 12.72 + 29 =
  13. 13.12 + 9 =
  14. 14.85 − 29 =
  15. 15.51 + 9 =
  16. 16.57 + 29 =
  17. 17.80 + 9 =
  18. 18.753 + 99 =
  19. 19.56 + 9 =
  20. 20.634 + 99 =
  21. 21.73 − 29 =
  22. 22.34 + 9 =
  23. 23.236 − 99 =
  24. 24.28 + 29 =
  25. 25.24 − 19 =
  26. 26.29 − 9 =
  27. 27.52 − 19 =
  28. 28.506 + 99 =
  29. 29.39 − 9 =
  30. 30.527 + 99 =
  31. 31.55 + 29 =
  32. 32.15 + 29 =
  33. 33.543 − 99 =
  34. 34.64 + 9 =
  35. 35.61 + 9 =
  36. 36.40 + 9 =
  37. 37.61 − 9 =
  38. 38.168 − 99 =
  39. 39.56 − 29 =
  40. 40.48 + 9 =

Answer key

  1. 13
  2. 846
  3. 24
  4. 601
  5. 14
  6. 54
  7. 96
  8. 92
  9. 49
  10. 4
  11. 887
  12. 101
  13. 21
  14. 56
  15. 60
  16. 86
  17. 89
  18. 852
  19. 65
  20. 733
  21. 44
  22. 43
  23. 137
  24. 57
  25. 5
  26. 20
  27. 33
  28. 605
  29. 30
  30. 626
  31. 84
  32. 44
  33. 444
  34. 73
  35. 70
  36. 49
  37. 52
  38. 69
  39. 27
  40. 57

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