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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 399 · 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. 2.39 − 19 =
  3. 3.281 + 99 =
  4. 4.269 − 99 =
  5. 5.83 − 19 =
  6. 6.106 − 29 =
  7. 7.67 − 29 =
  8. 8.44 + 29 =
  9. 9.73 − 29 =
  10. 10.66 + 9 =
  11. 11.43 − 19 =
  12. 12.87 − 19 =
  13. 13.23 + 9 =
  14. 14.46 + 29 =
  15. 15.203 − 99 =
  16. 16.44 − 19 =
  17. 17.34 − 9 =
  18. 18.85 − 19 =
  19. 19.686 − 99 =
  20. 20.498 − 99 =
  21. 21.36 − 19 =
  22. 22.29 − 9 =
  23. 23.72 + 19 =
  24. 24.92 − 19 =
  25. 25.749 + 99 =
  26. 26.54 + 9 =
  27. 27.296 − 99 =
  28. 28.105 − 29 =
  29. 29.73 + 9 =
  30. 30.53 − 9 =
  31. 31.78 − 19 =
  32. 32.78 + 29 =
  33. 33.50 − 29 =
  34. 34.838 − 99 =
  35. 35.72 + 29 =
  36. 36.65 + 9 =
  37. 37.43 + 9 =
  38. 38.27 + 19 =
  39. 39.511 − 99 =
  40. 40.68 + 29 =

Answer key

  1. 43
  2. 20
  3. 380
  4. 170
  5. 64
  6. 77
  7. 38
  8. 73
  9. 44
  10. 75
  11. 24
  12. 68
  13. 32
  14. 75
  15. 104
  16. 25
  17. 25
  18. 66
  19. 587
  20. 399
  21. 17
  22. 20
  23. 91
  24. 73
  25. 848
  26. 63
  27. 197
  28. 76
  29. 82
  30. 44
  31. 59
  32. 107
  33. 21
  34. 739
  35. 101
  36. 74
  37. 52
  38. 46
  39. 412
  40. 97

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