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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 247 · 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. 1.668 − 99 =
  2. 2.87 − 9 =
  3. 3.51 − 19 =
  4. 4.32 − 19 =
  5. 5.36 − 9 =
  6. 6.83 − 9 =
  7. 7.12 + 9 =
  8. 8.23 + 19 =
  9. 9.67 + 29 =
  10. 10.738 + 99 =
  11. 11.55 + 29 =
  12. 12.27 − 9 =
  13. 13.59 − 19 =
  14. 14.31 + 9 =
  15. 15.363 − 99 =
  16. 16.42 + 29 =
  17. 17.848 − 99 =
  18. 18.77 + 29 =
  19. 19.52 − 19 =
  20. 20.68 − 9 =
  21. 21.36 + 9 =
  22. 22.84 − 19 =
  23. 23.38 + 19 =
  24. 24.27 + 19 =
  25. 25.72 − 19 =
  26. 26.53 + 19 =
  27. 27.76 + 29 =
  28. 28.13 + 19 =
  29. 29.26 + 19 =
  30. 30.70 + 9 =
  31. 31.37 − 29 =
  32. 32.56 + 9 =
  33. 33.77 − 29 =
  34. 34.649 − 99 =
  35. 35.47 − 29 =
  36. 36.49 − 19 =
  37. 37.25 + 19 =
  38. 38.22 + 29 =
  39. 39.75 − 19 =
  40. 40.26 + 29 =

Answer key

  1. 569
  2. 78
  3. 32
  4. 13
  5. 27
  6. 74
  7. 21
  8. 42
  9. 96
  10. 837
  11. 84
  12. 18
  13. 40
  14. 40
  15. 264
  16. 71
  17. 749
  18. 106
  19. 33
  20. 59
  21. 45
  22. 65
  23. 57
  24. 46
  25. 53
  26. 72
  27. 105
  28. 32
  29. 45
  30. 79
  31. 8
  32. 65
  33. 48
  34. 550
  35. 18
  36. 30
  37. 44
  38. 51
  39. 56
  40. 55

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