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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 806 · 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. 1.306 − 99 =
  2. 2.34 + 19 =
  3. 3.18 − 9 =
  4. 4.84 − 9 =
  5. 5.57 − 9 =
  6. 6.64 − 9 =
  7. 7.30 + 29 =
  8. 8.88 − 29 =
  9. 9.429 − 99 =
  10. 10.23 − 9 =
  11. 11.46 + 9 =
  12. 12.39 + 9 =
  13. 13.617 + 99 =
  14. 14.65 − 19 =
  15. 15.18 + 19 =
  16. 16.654 + 99 =
  17. 17.527 + 99 =
  18. 18.41 + 9 =
  19. 19.19 − 9 =
  20. 20.71 − 9 =
  21. 21.30 − 9 =
  22. 22.677 + 99 =
  23. 23.37 − 9 =
  24. 24.26 + 19 =
  25. 25.65 − 9 =
  26. 26.56 − 9 =
  27. 27.35 − 19 =
  28. 28.49 + 29 =
  29. 29.85 − 19 =
  30. 30.217 − 99 =
  31. 31.63 + 19 =
  32. 32.12 + 9 =
  33. 33.15 + 29 =
  34. 34.378 − 99 =
  35. 35.30 + 19 =
  36. 36.76 − 9 =
  37. 37.296 + 99 =
  38. 38.51 + 9 =
  39. 39.274 − 99 =
  40. 40.740 + 99 =

Answer key

  1. 207
  2. 53
  3. 9
  4. 75
  5. 48
  6. 55
  7. 59
  8. 59
  9. 330
  10. 14
  11. 55
  12. 48
  13. 716
  14. 46
  15. 37
  16. 753
  17. 626
  18. 50
  19. 10
  20. 62
  21. 21
  22. 776
  23. 28
  24. 45
  25. 56
  26. 47
  27. 16
  28. 78
  29. 66
  30. 118
  31. 82
  32. 21
  33. 44
  34. 279
  35. 49
  36. 67
  37. 395
  38. 60
  39. 175
  40. 839

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