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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 497 · 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. 1.72 − 9 =
  2. 2.549 − 99 =
  3. 3.12 + 9 =
  4. 4.81 − 9 =
  5. 5.25 − 9 =
  6. 6.418 + 99 =
  7. 7.30 + 9 =
  8. 8.26 + 9 =
  9. 9.17 + 19 =
  10. 10.20 + 19 =
  11. 11.798 − 99 =
  12. 12.57 − 9 =
  13. 13.57 + 9 =
  14. 14.46 − 29 =
  15. 15.101 − 29 =
  16. 16.47 + 19 =
  17. 17.87 − 9 =
  18. 18.37 − 19 =
  19. 19.865 − 99 =
  20. 20.61 + 9 =
  21. 21.194 − 99 =
  22. 22.769 + 99 =
  23. 23.737 − 99 =
  24. 24.54 − 9 =
  25. 25.33 − 29 =
  26. 26.23 + 9 =
  27. 27.47 − 9 =
  28. 28.62 + 9 =
  29. 29.449 + 99 =
  30. 30.643 + 99 =
  31. 31.28 − 19 =
  32. 32.85 − 19 =
  33. 33.36 − 19 =
  34. 34.117 + 99 =
  35. 35.50 + 9 =
  36. 36.730 + 99 =
  37. 37.62 + 19 =
  38. 38.44 − 29 =
  39. 39.15 + 19 =
  40. 40.100 − 29 =

Answer key

  1. 63
  2. 450
  3. 21
  4. 72
  5. 16
  6. 517
  7. 39
  8. 35
  9. 36
  10. 39
  11. 699
  12. 48
  13. 66
  14. 17
  15. 72
  16. 66
  17. 78
  18. 18
  19. 766
  20. 70
  21. 95
  22. 868
  23. 638
  24. 45
  25. 4
  26. 32
  27. 38
  28. 71
  29. 548
  30. 742
  31. 9
  32. 66
  33. 17
  34. 216
  35. 59
  36. 829
  37. 81
  38. 15
  39. 34
  40. 71

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