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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 470 · 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. 1.69 − 9 =
  2. 2.72 + 29 =
  3. 3.94 − 29 =
  4. 4.217 − 99 =
  5. 5.245 + 99 =
  6. 6.14 + 19 =
  7. 7.831 − 99 =
  8. 8.223 + 99 =
  9. 9.597 − 99 =
  10. 10.108 − 29 =
  11. 11.50 − 29 =
  12. 12.29 + 29 =
  13. 13.19 + 9 =
  14. 14.25 − 9 =
  15. 15.67 − 9 =
  16. 16.55 + 19 =
  17. 17.209 − 99 =
  18. 18.58 + 19 =
  19. 19.32 − 19 =
  20. 20.63 + 9 =
  21. 21.60 + 19 =
  22. 22.175 − 99 =
  23. 23.74 + 9 =
  24. 24.84 − 9 =
  25. 25.93 − 29 =
  26. 26.67 + 19 =
  27. 27.38 − 29 =
  28. 28.765 + 99 =
  29. 29.31 + 9 =
  30. 30.99 − 19 =
  31. 31.427 + 99 =
  32. 32.96 − 19 =
  33. 33.47 − 29 =
  34. 34.63 − 9 =
  35. 35.29 + 9 =
  36. 36.140 + 99 =
  37. 37.587 + 99 =
  38. 38.438 + 99 =
  39. 39.40 + 9 =
  40. 40.152 + 99 =

Answer key

  1. 60
  2. 101
  3. 65
  4. 118
  5. 344
  6. 33
  7. 732
  8. 322
  9. 498
  10. 79
  11. 21
  12. 58
  13. 28
  14. 16
  15. 58
  16. 74
  17. 110
  18. 77
  19. 13
  20. 72
  21. 79
  22. 76
  23. 83
  24. 75
  25. 64
  26. 86
  27. 9
  28. 864
  29. 40
  30. 80
  31. 526
  32. 77
  33. 18
  34. 54
  35. 38
  36. 239
  37. 686
  38. 537
  39. 49
  40. 251

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