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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 873 · 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 − 19 =
  2. 2.28 + 9 =
  3. 3.72 + 9 =
  4. 4.49 − 29 =
  5. 5.14 + 29 =
  6. 6.47 + 29 =
  7. 7.27 + 9 =
  8. 8.816 − 99 =
  9. 9.731 + 99 =
  10. 10.601 + 99 =
  11. 11.76 + 9 =
  12. 12.88 − 9 =
  13. 13.43 + 9 =
  14. 14.103 − 29 =
  15. 15.22 − 19 =
  16. 16.64 + 9 =
  17. 17.751 + 99 =
  18. 18.16 + 9 =
  19. 19.54 − 29 =
  20. 20.323 − 99 =
  21. 21.49 + 9 =
  22. 22.26 + 29 =
  23. 23.85 − 19 =
  24. 24.180 − 99 =
  25. 25.67 − 19 =
  26. 26.19 + 29 =
  27. 27.668 − 99 =
  28. 28.40 + 19 =
  29. 29.58 − 19 =
  30. 30.15 − 9 =
  31. 31.30 + 29 =
  32. 32.57 + 19 =
  33. 33.53 + 9 =
  34. 34.24 + 9 =
  35. 35.74 + 9 =
  36. 36.768 + 99 =
  37. 37.193 − 99 =
  38. 38.159 − 99 =
  39. 39.62 − 29 =
  40. 40.51 + 29 =

Answer key

  1. 23
  2. 37
  3. 81
  4. 20
  5. 43
  6. 76
  7. 36
  8. 717
  9. 830
  10. 700
  11. 85
  12. 79
  13. 52
  14. 74
  15. 3
  16. 73
  17. 850
  18. 25
  19. 25
  20. 224
  21. 58
  22. 55
  23. 66
  24. 81
  25. 48
  26. 48
  27. 569
  28. 59
  29. 39
  30. 6
  31. 59
  32. 76
  33. 62
  34. 33
  35. 83
  36. 867
  37. 94
  38. 60
  39. 33
  40. 80

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