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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 589 · 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. 1.49 − 19 =
  2. 2.35 + 9 =
  3. 3.46 − 9 =
  4. 4.222 + 99 =
  5. 5.624 + 99 =
  6. 6.32 + 19 =
  7. 7.18 + 19 =
  8. 8.506 − 99 =
  9. 9.89 − 19 =
  10. 10.634 − 99 =
  11. 11.44 + 9 =
  12. 12.39 − 29 =
  13. 13.35 + 19 =
  14. 14.66 − 9 =
  15. 15.60 + 9 =
  16. 16.482 + 99 =
  17. 17.14 + 9 =
  18. 18.34 + 9 =
  19. 19.769 + 99 =
  20. 20.17 + 19 =
  21. 21.37 − 19 =
  22. 22.21 + 29 =
  23. 23.42 − 19 =
  24. 24.85 − 29 =
  25. 25.79 + 9 =
  26. 26.50 − 9 =
  27. 27.76 + 29 =
  28. 28.68 − 19 =
  29. 29.15 + 29 =
  30. 30.45 − 9 =
  31. 31.31 − 9 =
  32. 32.70 + 29 =
  33. 33.22 − 19 =
  34. 34.713 + 99 =
  35. 35.72 − 9 =
  36. 36.358 − 99 =
  37. 37.51 − 19 =
  38. 38.61 − 19 =
  39. 39.624 − 99 =
  40. 40.12 + 29 =

Answer key

  1. 30
  2. 44
  3. 37
  4. 321
  5. 723
  6. 51
  7. 37
  8. 407
  9. 70
  10. 535
  11. 53
  12. 10
  13. 54
  14. 57
  15. 69
  16. 581
  17. 23
  18. 43
  19. 868
  20. 36
  21. 18
  22. 50
  23. 23
  24. 56
  25. 88
  26. 41
  27. 105
  28. 49
  29. 44
  30. 36
  31. 22
  32. 99
  33. 3
  34. 812
  35. 63
  36. 259
  37. 32
  38. 42
  39. 525
  40. 41

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