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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 568 · 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. 1.66 − 29 =
  2. 2.30 + 19 =
  3. 3.24 − 19 =
  4. 4.676 + 99 =
  5. 5.34 − 9 =
  6. 6.44 + 9 =
  7. 7.569 − 99 =
  8. 8.73 + 29 =
  9. 9.58 + 19 =
  10. 10.347 + 99 =
  11. 11.105 − 29 =
  12. 12.20 − 9 =
  13. 13.76 + 9 =
  14. 14.20 + 9 =
  15. 15.35 − 29 =
  16. 16.99 − 19 =
  17. 17.362 − 99 =
  18. 18.84 − 19 =
  19. 19.566 − 99 =
  20. 20.33 − 9 =
  21. 21.75 + 29 =
  22. 22.269 + 99 =
  23. 23.181 + 99 =
  24. 24.391 + 99 =
  25. 25.81 − 29 =
  26. 26.28 + 9 =
  27. 27.84 − 9 =
  28. 28.622 − 99 =
  29. 29.56 + 9 =
  30. 30.50 + 9 =
  31. 31.42 + 19 =
  32. 32.38 − 9 =
  33. 33.26 + 9 =
  34. 34.62 + 29 =
  35. 35.14 + 9 =
  36. 36.134 + 99 =
  37. 37.27 + 29 =
  38. 38.23 − 9 =
  39. 39.384 + 99 =
  40. 40.32 + 9 =

Answer key

  1. 37
  2. 49
  3. 5
  4. 775
  5. 25
  6. 53
  7. 470
  8. 102
  9. 77
  10. 446
  11. 76
  12. 11
  13. 85
  14. 29
  15. 6
  16. 80
  17. 263
  18. 65
  19. 467
  20. 24
  21. 104
  22. 368
  23. 280
  24. 490
  25. 52
  26. 37
  27. 75
  28. 523
  29. 65
  30. 59
  31. 61
  32. 29
  33. 35
  34. 91
  35. 23
  36. 233
  37. 56
  38. 14
  39. 483
  40. 41

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