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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 180 · 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. 1.80 + 19 =
  2. 2.76 + 9 =
  3. 3.79 − 29 =
  4. 4.75 − 29 =
  5. 5.32 − 19 =
  6. 6.30 − 19 =
  7. 7.153 + 99 =
  8. 8.30 − 9 =
  9. 9.57 + 29 =
  10. 10.93 − 29 =
  11. 11.74 + 9 =
  12. 12.56 + 19 =
  13. 13.391 − 99 =
  14. 14.28 + 9 =
  15. 15.422 − 99 =
  16. 16.55 + 9 =
  17. 17.23 + 29 =
  18. 18.22 − 19 =
  19. 19.66 + 9 =
  20. 20.39 − 29 =
  21. 21.62 − 9 =
  22. 22.25 + 9 =
  23. 23.14 + 9 =
  24. 24.46 + 9 =
  25. 25.58 − 9 =
  26. 26.274 + 99 =
  27. 27.47 + 19 =
  28. 28.57 + 9 =
  29. 29.33 + 9 =
  30. 30.39 + 29 =
  31. 31.95 − 19 =
  32. 32.71 − 9 =
  33. 33.91 − 29 =
  34. 34.673 + 99 =
  35. 35.365 + 99 =
  36. 36.592 + 99 =
  37. 37.44 + 19 =
  38. 38.36 + 9 =
  39. 39.313 − 99 =
  40. 40.28 − 9 =

Answer key

  1. 99
  2. 85
  3. 50
  4. 46
  5. 13
  6. 11
  7. 252
  8. 21
  9. 86
  10. 64
  11. 83
  12. 75
  13. 292
  14. 37
  15. 323
  16. 64
  17. 52
  18. 3
  19. 75
  20. 10
  21. 53
  22. 34
  23. 23
  24. 55
  25. 49
  26. 373
  27. 66
  28. 66
  29. 42
  30. 68
  31. 76
  32. 62
  33. 62
  34. 772
  35. 464
  36. 691
  37. 63
  38. 45
  39. 214
  40. 19

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