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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 595 · 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. 1.64 + 29 =
  2. 2.43 + 9 =
  3. 3.47 − 19 =
  4. 4.75 − 9 =
  5. 5.798 − 99 =
  6. 6.30 + 19 =
  7. 7.29 + 9 =
  8. 8.22 − 9 =
  9. 9.232 + 99 =
  10. 10.17 + 9 =
  11. 11.63 − 29 =
  12. 12.77 − 9 =
  13. 13.44 + 9 =
  14. 14.672 + 99 =
  15. 15.207 + 99 =
  16. 16.39 + 19 =
  17. 17.47 − 29 =
  18. 18.71 + 29 =
  19. 19.29 + 29 =
  20. 20.65 + 19 =
  21. 21.700 − 99 =
  22. 22.79 + 9 =
  23. 23.13 + 29 =
  24. 24.26 + 9 =
  25. 25.716 − 99 =
  26. 26.15 − 9 =
  27. 27.49 + 29 =
  28. 28.76 + 9 =
  29. 29.54 + 9 =
  30. 30.642 + 99 =
  31. 31.24 − 9 =
  32. 32.56 − 19 =
  33. 33.15 + 19 =
  34. 34.743 + 99 =
  35. 35.54 − 9 =
  36. 36.95 − 19 =
  37. 37.88 − 9 =
  38. 38.50 + 9 =
  39. 39.406 + 99 =
  40. 40.50 + 19 =

Answer key

  1. 93
  2. 52
  3. 28
  4. 66
  5. 699
  6. 49
  7. 38
  8. 13
  9. 331
  10. 26
  11. 34
  12. 68
  13. 53
  14. 771
  15. 306
  16. 58
  17. 18
  18. 100
  19. 58
  20. 84
  21. 601
  22. 88
  23. 42
  24. 35
  25. 617
  26. 6
  27. 78
  28. 85
  29. 63
  30. 741
  31. 15
  32. 37
  33. 34
  34. 842
  35. 45
  36. 76
  37. 79
  38. 59
  39. 505
  40. 69

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