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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 919 · 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. 1.83 − 29 =
  2. 2.104 − 29 =
  3. 3.12 + 19 =
  4. 4.429 + 99 =
  5. 5.48 − 9 =
  6. 6.60 − 19 =
  7. 7.62 + 19 =
  8. 8.306 − 99 =
  9. 9.41 + 9 =
  10. 10.54 − 29 =
  11. 11.37 − 29 =
  12. 12.34 − 29 =
  13. 13.72 − 29 =
  14. 14.78 − 19 =
  15. 15.761 − 99 =
  16. 16.476 + 99 =
  17. 17.24 − 9 =
  18. 18.60 − 9 =
  19. 19.725 + 99 =
  20. 20.73 + 19 =
  21. 21.14 + 19 =
  22. 22.730 + 99 =
  23. 23.63 + 9 =
  24. 24.17 + 19 =
  25. 25.42 − 19 =
  26. 26.79 − 19 =
  27. 27.31 + 19 =
  28. 28.185 − 99 =
  29. 29.42 + 9 =
  30. 30.628 + 99 =
  31. 31.21 + 9 =
  32. 32.48 + 29 =
  33. 33.631 − 99 =
  34. 34.533 − 99 =
  35. 35.99 − 19 =
  36. 36.24 + 9 =
  37. 37.107 − 29 =
  38. 38.33 + 29 =
  39. 39.121 + 99 =
  40. 40.60 + 29 =

Answer key

  1. 54
  2. 75
  3. 31
  4. 528
  5. 39
  6. 41
  7. 81
  8. 207
  9. 50
  10. 25
  11. 8
  12. 5
  13. 43
  14. 59
  15. 662
  16. 575
  17. 15
  18. 51
  19. 824
  20. 92
  21. 33
  22. 829
  23. 72
  24. 36
  25. 23
  26. 60
  27. 50
  28. 86
  29. 51
  30. 727
  31. 30
  32. 77
  33. 532
  34. 434
  35. 80
  36. 33
  37. 78
  38. 62
  39. 220
  40. 89

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