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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 106 · 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. 1.14 + 29 =
  2. 2.16 + 29 =
  3. 3.66 + 9 =
  4. 4.78 + 19 =
  5. 5.90 − 19 =
  6. 6.19 + 9 =
  7. 7.65 − 9 =
  8. 8.22 − 9 =
  9. 9.54 + 29 =
  10. 10.764 + 99 =
  11. 11.81 − 29 =
  12. 12.632 + 99 =
  13. 13.17 + 19 =
  14. 14.89 − 29 =
  15. 15.107 − 29 =
  16. 16.12 + 29 =
  17. 17.13 − 9 =
  18. 18.30 + 9 =
  19. 19.24 − 9 =
  20. 20.51 + 9 =
  21. 21.86 − 29 =
  22. 22.36 + 19 =
  23. 23.66 − 9 =
  24. 24.359 + 99 =
  25. 25.65 + 19 =
  26. 26.69 + 9 =
  27. 27.456 − 99 =
  28. 28.52 + 19 =
  29. 29.77 − 19 =
  30. 30.578 + 99 =
  31. 31.29 − 19 =
  32. 32.863 − 99 =
  33. 33.41 + 29 =
  34. 34.586 + 99 =
  35. 35.84 − 29 =
  36. 36.34 − 9 =
  37. 37.15 + 9 =
  38. 38.729 − 99 =
  39. 39.352 + 99 =
  40. 40.68 − 19 =

Answer key

  1. 43
  2. 45
  3. 75
  4. 97
  5. 71
  6. 28
  7. 56
  8. 13
  9. 83
  10. 863
  11. 52
  12. 731
  13. 36
  14. 60
  15. 78
  16. 41
  17. 4
  18. 39
  19. 15
  20. 60
  21. 57
  22. 55
  23. 57
  24. 458
  25. 84
  26. 78
  27. 357
  28. 71
  29. 58
  30. 677
  31. 10
  32. 764
  33. 70
  34. 685
  35. 55
  36. 25
  37. 24
  38. 630
  39. 451
  40. 49

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