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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 613 · 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. 1.69 − 9 =
  2. 2.66 − 19 =
  3. 3.77 − 29 =
  4. 4.39 + 19 =
  5. 5.50 + 29 =
  6. 6.59 − 9 =
  7. 7.28 − 9 =
  8. 8.66 + 29 =
  9. 9.22 + 19 =
  10. 10.19 + 19 =
  11. 11.71 + 29 =
  12. 12.328 + 99 =
  13. 13.61 + 29 =
  14. 14.80 + 9 =
  15. 15.619 − 99 =
  16. 16.62 + 29 =
  17. 17.23 − 9 =
  18. 18.67 + 29 =
  19. 19.14 + 29 =
  20. 20.105 + 99 =
  21. 21.88 − 9 =
  22. 22.44 − 9 =
  23. 23.48 + 9 =
  24. 24.689 + 99 =
  25. 25.64 − 19 =
  26. 26.14 − 9 =
  27. 27.79 + 9 =
  28. 28.24 + 9 =
  29. 29.33 + 9 =
  30. 30.640 − 99 =
  31. 31.245 + 99 =
  32. 32.358 + 99 =
  33. 33.660 + 99 =
  34. 34.19 + 29 =
  35. 35.85 − 29 =
  36. 36.36 + 19 =
  37. 37.36 − 9 =
  38. 38.174 + 99 =
  39. 39.47 + 9 =
  40. 40.26 + 29 =

Answer key

  1. 60
  2. 47
  3. 48
  4. 58
  5. 79
  6. 50
  7. 19
  8. 95
  9. 41
  10. 38
  11. 100
  12. 427
  13. 90
  14. 89
  15. 520
  16. 91
  17. 14
  18. 96
  19. 43
  20. 204
  21. 79
  22. 35
  23. 57
  24. 788
  25. 45
  26. 5
  27. 88
  28. 33
  29. 42
  30. 541
  31. 344
  32. 457
  33. 759
  34. 48
  35. 56
  36. 55
  37. 27
  38. 273
  39. 56
  40. 55

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