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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 439 · 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. 1.59 − 29 =
  2. 2.20 − 9 =
  3. 3.103 − 29 =
  4. 4.21 + 19 =
  5. 5.34 − 29 =
  6. 6.73 − 19 =
  7. 7.68 − 29 =
  8. 8.13 + 9 =
  9. 9.39 + 29 =
  10. 10.33 + 29 =
  11. 11.158 + 99 =
  12. 12.49 + 19 =
  13. 13.74 − 19 =
  14. 14.625 + 99 =
  15. 15.18 + 19 =
  16. 16.99 − 19 =
  17. 17.62 − 29 =
  18. 18.56 + 19 =
  19. 19.57 + 9 =
  20. 20.29 + 29 =
  21. 21.689 + 99 =
  22. 22.61 − 9 =
  23. 23.34 − 19 =
  24. 24.24 − 9 =
  25. 25.31 − 19 =
  26. 26.71 + 9 =
  27. 27.48 + 9 =
  28. 28.727 + 99 =
  29. 29.36 + 19 =
  30. 30.47 + 29 =
  31. 31.44 − 29 =
  32. 32.369 − 99 =
  33. 33.32 + 29 =
  34. 34.39 − 29 =
  35. 35.54 − 9 =
  36. 36.56 + 29 =
  37. 37.59 + 9 =
  38. 38.40 + 19 =
  39. 39.28 + 9 =
  40. 40.41 − 9 =

Answer key

  1. 30
  2. 11
  3. 74
  4. 40
  5. 5
  6. 54
  7. 39
  8. 22
  9. 68
  10. 62
  11. 257
  12. 68
  13. 55
  14. 724
  15. 37
  16. 80
  17. 33
  18. 75
  19. 66
  20. 58
  21. 788
  22. 52
  23. 15
  24. 15
  25. 12
  26. 80
  27. 57
  28. 826
  29. 55
  30. 76
  31. 15
  32. 270
  33. 61
  34. 10
  35. 45
  36. 85
  37. 68
  38. 59
  39. 37
  40. 32

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