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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 888 · 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. 1.42 + 9 =
  2. 2.67 − 19 =
  3. 3.16 + 29 =
  4. 4.37 + 9 =
  5. 5.46 + 29 =
  6. 6.60 + 19 =
  7. 7.72 + 9 =
  8. 8.36 − 9 =
  9. 9.25 + 19 =
  10. 10.61 − 19 =
  11. 11.741 − 99 =
  12. 12.69 − 29 =
  13. 13.84 − 29 =
  14. 14.65 − 19 =
  15. 15.50 + 29 =
  16. 16.47 − 9 =
  17. 17.35 + 9 =
  18. 18.41 + 19 =
  19. 19.107 − 29 =
  20. 20.388 + 99 =
  21. 21.679 + 99 =
  22. 22.44 + 9 =
  23. 23.29 + 9 =
  24. 24.27 + 9 =
  25. 25.88 − 19 =
  26. 26.45 − 9 =
  27. 27.94 − 29 =
  28. 28.108 − 29 =
  29. 29.68 + 9 =
  30. 30.50 − 9 =
  31. 31.69 + 29 =
  32. 32.24 − 19 =
  33. 33.456 − 99 =
  34. 34.27 − 19 =
  35. 35.78 + 19 =
  36. 36.39 − 9 =
  37. 37.62 − 9 =
  38. 38.426 + 99 =
  39. 39.89 − 9 =
  40. 40.49 − 19 =

Answer key

  1. 51
  2. 48
  3. 45
  4. 46
  5. 75
  6. 79
  7. 81
  8. 27
  9. 44
  10. 42
  11. 642
  12. 40
  13. 55
  14. 46
  15. 79
  16. 38
  17. 44
  18. 60
  19. 78
  20. 487
  21. 778
  22. 53
  23. 38
  24. 36
  25. 69
  26. 36
  27. 65
  28. 79
  29. 77
  30. 41
  31. 98
  32. 5
  33. 357
  34. 8
  35. 97
  36. 30
  37. 53
  38. 525
  39. 80
  40. 30

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