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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 265 · 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. 1.13 + 19 =
  2. 2.34 − 9 =
  3. 3.70 + 19 =
  4. 4.32 − 9 =
  5. 5.18 + 29 =
  6. 6.53 + 19 =
  7. 7.50 + 9 =
  8. 8.24 − 9 =
  9. 9.647 + 99 =
  10. 10.107 − 29 =
  11. 11.77 − 29 =
  12. 12.46 − 9 =
  13. 13.78 + 9 =
  14. 14.100 − 29 =
  15. 15.49 + 9 =
  16. 16.15 + 19 =
  17. 17.65 + 9 =
  18. 18.67 − 9 =
  19. 19.18 + 19 =
  20. 20.760 − 99 =
  21. 21.85 − 29 =
  22. 22.79 + 29 =
  23. 23.12 + 9 =
  24. 24.86 − 9 =
  25. 25.52 + 19 =
  26. 26.33 + 29 =
  27. 27.41 − 29 =
  28. 28.75 + 19 =
  29. 29.722 + 99 =
  30. 30.682 + 99 =
  31. 31.62 + 9 =
  32. 32.724 − 99 =
  33. 33.52 + 9 =
  34. 34.19 − 9 =
  35. 35.39 + 29 =
  36. 36.95 − 29 =
  37. 37.452 + 99 =
  38. 38.619 − 99 =
  39. 39.27 + 9 =
  40. 40.48 − 9 =

Answer key

  1. 32
  2. 25
  3. 89
  4. 23
  5. 47
  6. 72
  7. 59
  8. 15
  9. 746
  10. 78
  11. 48
  12. 37
  13. 87
  14. 71
  15. 58
  16. 34
  17. 74
  18. 58
  19. 37
  20. 661
  21. 56
  22. 108
  23. 21
  24. 77
  25. 71
  26. 62
  27. 12
  28. 94
  29. 821
  30. 781
  31. 71
  32. 625
  33. 61
  34. 10
  35. 68
  36. 66
  37. 551
  38. 520
  39. 36
  40. 39

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