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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 356 · 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. 1.84 − 9 =
  2. 2.57 + 9 =
  3. 3.62 + 9 =
  4. 4.59 + 9 =
  5. 5.50 + 19 =
  6. 6.40 + 9 =
  7. 7.89 − 9 =
  8. 8.26 + 9 =
  9. 9.75 + 19 =
  10. 10.56 + 29 =
  11. 11.31 + 9 =
  12. 12.61 + 29 =
  13. 13.129 + 99 =
  14. 14.241 + 99 =
  15. 15.65 − 9 =
  16. 16.37 + 9 =
  17. 17.29 − 19 =
  18. 18.37 + 19 =
  19. 19.484 − 99 =
  20. 20.51 + 9 =
  21. 21.266 + 99 =
  22. 22.29 − 9 =
  23. 23.47 − 19 =
  24. 24.543 − 99 =
  25. 25.23 + 19 =
  26. 26.39 − 29 =
  27. 27.41 − 19 =
  28. 28.22 − 19 =
  29. 29.272 − 99 =
  30. 30.73 − 19 =
  31. 31.537 − 99 =
  32. 32.174 + 99 =
  33. 33.48 + 19 =
  34. 34.77 + 9 =
  35. 35.490 + 99 =
  36. 36.54 + 19 =
  37. 37.501 + 99 =
  38. 38.14 − 9 =
  39. 39.43 − 19 =
  40. 40.17 + 9 =

Answer key

  1. 75
  2. 66
  3. 71
  4. 68
  5. 69
  6. 49
  7. 80
  8. 35
  9. 94
  10. 85
  11. 40
  12. 90
  13. 228
  14. 340
  15. 56
  16. 46
  17. 10
  18. 56
  19. 385
  20. 60
  21. 365
  22. 20
  23. 28
  24. 444
  25. 42
  26. 10
  27. 22
  28. 3
  29. 173
  30. 54
  31. 438
  32. 273
  33. 67
  34. 86
  35. 589
  36. 73
  37. 600
  38. 5
  39. 24
  40. 26

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