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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 164 · 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. 1.69 + 19 =
  2. 2.41 + 19 =
  3. 3.97 − 19 =
  4. 4.60 + 9 =
  5. 5.452 − 99 =
  6. 6.78 + 9 =
  7. 7.391 + 99 =
  8. 8.703 − 99 =
  9. 9.44 + 9 =
  10. 10.46 − 9 =
  11. 11.50 + 29 =
  12. 12.109 + 99 =
  13. 13.29 + 29 =
  14. 14.133 + 99 =
  15. 15.13 + 9 =
  16. 16.50 + 19 =
  17. 17.22 + 9 =
  18. 18.76 + 9 =
  19. 19.46 + 29 =
  20. 20.88 − 19 =
  21. 21.57 − 19 =
  22. 22.326 − 99 =
  23. 23.84 − 29 =
  24. 24.54 + 19 =
  25. 25.108 − 29 =
  26. 26.72 − 19 =
  27. 27.454 − 99 =
  28. 28.19 + 9 =
  29. 29.83 − 9 =
  30. 30.684 − 99 =
  31. 31.26 + 9 =
  32. 32.82 − 9 =
  33. 33.520 − 99 =
  34. 34.28 − 9 =
  35. 35.67 + 9 =
  36. 36.70 − 29 =
  37. 37.88 − 9 =
  38. 38.52 + 9 =
  39. 39.50 + 9 =
  40. 40.42 − 29 =

Answer key

  1. 88
  2. 60
  3. 78
  4. 69
  5. 353
  6. 87
  7. 490
  8. 604
  9. 53
  10. 37
  11. 79
  12. 208
  13. 58
  14. 232
  15. 22
  16. 69
  17. 31
  18. 85
  19. 75
  20. 69
  21. 38
  22. 227
  23. 55
  24. 73
  25. 79
  26. 53
  27. 355
  28. 28
  29. 74
  30. 585
  31. 35
  32. 73
  33. 421
  34. 19
  35. 76
  36. 41
  37. 79
  38. 61
  39. 59
  40. 13

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