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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 122 · 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 + 29 =
  2. 2.16 + 29 =
  3. 3.788 − 99 =
  4. 4.91 − 29 =
  5. 5.48 − 19 =
  6. 6.23 + 9 =
  7. 7.31 + 29 =
  8. 8.31 − 9 =
  9. 9.72 + 29 =
  10. 10.90 − 29 =
  11. 11.299 + 99 =
  12. 12.82 − 9 =
  13. 13.45 + 19 =
  14. 14.81 − 29 =
  15. 15.71 + 19 =
  16. 16.61 + 9 =
  17. 17.623 − 99 =
  18. 18.651 + 99 =
  19. 19.222 − 99 =
  20. 20.32 + 9 =
  21. 21.17 + 9 =
  22. 22.26 + 9 =
  23. 23.86 − 9 =
  24. 24.63 + 9 =
  25. 25.780 − 99 =
  26. 26.39 − 19 =
  27. 27.12 + 19 =
  28. 28.39 − 9 =
  29. 29.64 + 19 =
  30. 30.55 + 29 =
  31. 31.699 + 99 =
  32. 32.67 + 29 =
  33. 33.62 − 19 =
  34. 34.14 + 19 =
  35. 35.24 + 9 =
  36. 36.33 − 19 =
  37. 37.33 + 19 =
  38. 38.587 + 99 =
  39. 39.32 + 19 =
  40. 40.31 + 9 =

Answer key

  1. 71
  2. 45
  3. 689
  4. 62
  5. 29
  6. 32
  7. 60
  8. 22
  9. 101
  10. 61
  11. 398
  12. 73
  13. 64
  14. 52
  15. 90
  16. 70
  17. 524
  18. 750
  19. 123
  20. 41
  21. 26
  22. 35
  23. 77
  24. 72
  25. 681
  26. 20
  27. 31
  28. 30
  29. 83
  30. 84
  31. 798
  32. 96
  33. 43
  34. 33
  35. 33
  36. 14
  37. 52
  38. 686
  39. 51
  40. 40

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