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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 87 · 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. 1.29 − 19 =
  2. 2.695 − 99 =
  3. 3.575 + 99 =
  4. 4.75 + 9 =
  5. 5.24 − 9 =
  6. 6.41 − 19 =
  7. 7.305 + 99 =
  8. 8.37 + 29 =
  9. 9.33 − 29 =
  10. 10.77 − 19 =
  11. 11.57 − 29 =
  12. 12.282 − 99 =
  13. 13.15 + 9 =
  14. 14.333 − 99 =
  15. 15.39 + 29 =
  16. 16.723 + 99 =
  17. 17.37 − 29 =
  18. 18.588 + 99 =
  19. 19.35 + 19 =
  20. 20.390 − 99 =
  21. 21.62 + 29 =
  22. 22.45 + 19 =
  23. 23.88 − 19 =
  24. 24.59 + 19 =
  25. 25.13 + 9 =
  26. 26.306 − 99 =
  27. 27.30 + 29 =
  28. 28.76 + 29 =
  29. 29.86 − 19 =
  30. 30.63 − 9 =
  31. 31.44 − 29 =
  32. 32.115 + 99 =
  33. 33.15 + 29 =
  34. 34.485 + 99 =
  35. 35.17 + 9 =
  36. 36.55 − 19 =
  37. 37.64 − 19 =
  38. 38.90 − 19 =
  39. 39.28 + 29 =
  40. 40.194 − 99 =

Answer key

  1. 10
  2. 596
  3. 674
  4. 84
  5. 15
  6. 22
  7. 404
  8. 66
  9. 4
  10. 58
  11. 28
  12. 183
  13. 24
  14. 234
  15. 68
  16. 822
  17. 8
  18. 687
  19. 54
  20. 291
  21. 91
  22. 64
  23. 69
  24. 78
  25. 22
  26. 207
  27. 59
  28. 105
  29. 67
  30. 54
  31. 15
  32. 214
  33. 44
  34. 584
  35. 26
  36. 36
  37. 45
  38. 71
  39. 57
  40. 95

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