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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 63 · 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. 1.75 + 19 =
  2. 2.63 − 9 =
  3. 3.50 + 29 =
  4. 4.807 − 99 =
  5. 5.72 − 29 =
  6. 6.70 − 9 =
  7. 7.72 + 9 =
  8. 8.14 + 29 =
  9. 9.26 + 9 =
  10. 10.648 + 99 =
  11. 11.694 + 99 =
  12. 12.52 − 9 =
  13. 13.64 − 29 =
  14. 14.57 + 19 =
  15. 15.22 + 9 =
  16. 16.59 − 9 =
  17. 17.86 − 9 =
  18. 18.53 + 9 =
  19. 19.531 − 99 =
  20. 20.31 − 9 =
  21. 21.32 + 19 =
  22. 22.69 − 29 =
  23. 23.430 − 99 =
  24. 24.17 + 19 =
  25. 25.83 − 9 =
  26. 26.65 + 19 =
  27. 27.65 + 9 =
  28. 28.860 − 99 =
  29. 29.51 + 9 =
  30. 30.37 + 29 =
  31. 31.28 + 19 =
  32. 32.80 − 9 =
  33. 33.79 + 9 =
  34. 34.75 + 29 =
  35. 35.79 + 29 =
  36. 36.74 + 9 =
  37. 37.31 + 19 =
  38. 38.731 + 99 =
  39. 39.31 + 9 =
  40. 40.56 + 19 =

Answer key

  1. 94
  2. 54
  3. 79
  4. 708
  5. 43
  6. 61
  7. 81
  8. 43
  9. 35
  10. 747
  11. 793
  12. 43
  13. 35
  14. 76
  15. 31
  16. 50
  17. 77
  18. 62
  19. 432
  20. 22
  21. 51
  22. 40
  23. 331
  24. 36
  25. 74
  26. 84
  27. 74
  28. 761
  29. 60
  30. 66
  31. 47
  32. 71
  33. 88
  34. 104
  35. 108
  36. 83
  37. 50
  38. 830
  39. 40
  40. 75

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