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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 446 · 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. 1.36 + 19 =
  2. 2.44 − 9 =
  3. 3.882 − 99 =
  4. 4.52 − 9 =
  5. 5.29 + 9 =
  6. 6.98 − 29 =
  7. 7.80 − 9 =
  8. 8.59 − 9 =
  9. 9.59 − 19 =
  10. 10.64 − 9 =
  11. 11.313 + 99 =
  12. 12.73 + 19 =
  13. 13.70 − 29 =
  14. 14.19 + 19 =
  15. 15.159 − 99 =
  16. 16.783 + 99 =
  17. 17.66 + 19 =
  18. 18.32 − 19 =
  19. 19.60 − 19 =
  20. 20.184 − 99 =
  21. 21.72 + 29 =
  22. 22.69 − 29 =
  23. 23.363 + 99 =
  24. 24.24 + 19 =
  25. 25.95 − 19 =
  26. 26.73 + 29 =
  27. 27.37 + 19 =
  28. 28.229 + 99 =
  29. 29.737 − 99 =
  30. 30.12 + 19 =
  31. 31.74 + 19 =
  32. 32.75 + 9 =
  33. 33.778 + 99 =
  34. 34.42 + 9 =
  35. 35.178 − 99 =
  36. 36.67 + 19 =
  37. 37.78 + 19 =
  38. 38.38 + 9 =
  39. 39.66 + 9 =
  40. 40.16 + 29 =

Answer key

  1. 55
  2. 35
  3. 783
  4. 43
  5. 38
  6. 69
  7. 71
  8. 50
  9. 40
  10. 55
  11. 412
  12. 92
  13. 41
  14. 38
  15. 60
  16. 882
  17. 85
  18. 13
  19. 41
  20. 85
  21. 101
  22. 40
  23. 462
  24. 43
  25. 76
  26. 102
  27. 56
  28. 328
  29. 638
  30. 31
  31. 93
  32. 84
  33. 877
  34. 51
  35. 79
  36. 86
  37. 97
  38. 47
  39. 75
  40. 45

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