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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 777 · 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. 1.88 − 9 =
  2. 2.26 − 19 =
  3. 3.49 + 9 =
  4. 4.68 − 19 =
  5. 5.57 + 9 =
  6. 6.704 − 99 =
  7. 7.96 − 19 =
  8. 8.23 + 29 =
  9. 9.30 + 19 =
  10. 10.44 − 9 =
  11. 11.466 − 99 =
  12. 12.624 − 99 =
  13. 13.750 + 99 =
  14. 14.28 + 29 =
  15. 15.62 − 29 =
  16. 16.48 − 9 =
  17. 17.38 + 9 =
  18. 18.56 + 19 =
  19. 19.89 − 29 =
  20. 20.64 + 29 =
  21. 21.69 + 9 =
  22. 22.650 − 99 =
  23. 23.665 − 99 =
  24. 24.302 + 99 =
  25. 25.191 + 99 =
  26. 26.763 + 99 =
  27. 27.13 − 9 =
  28. 28.74 + 29 =
  29. 29.30 + 9 =
  30. 30.63 + 9 =
  31. 31.29 − 9 =
  32. 32.780 − 99 =
  33. 33.68 + 19 =
  34. 34.713 + 99 =
  35. 35.67 − 19 =
  36. 36.14 + 9 =
  37. 37.44 + 29 =
  38. 38.676 + 99 =
  39. 39.353 + 99 =
  40. 40.795 − 99 =

Answer key

  1. 79
  2. 7
  3. 58
  4. 49
  5. 66
  6. 605
  7. 77
  8. 52
  9. 49
  10. 35
  11. 367
  12. 525
  13. 849
  14. 57
  15. 33
  16. 39
  17. 47
  18. 75
  19. 60
  20. 93
  21. 78
  22. 551
  23. 566
  24. 401
  25. 290
  26. 862
  27. 4
  28. 103
  29. 39
  30. 72
  31. 20
  32. 681
  33. 87
  34. 812
  35. 48
  36. 23
  37. 73
  38. 775
  39. 452
  40. 696

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