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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 707 · 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. 1.86 − 9 =
  2. 2.41 + 29 =
  3. 3.463 + 99 =
  4. 4.78 + 29 =
  5. 5.576 + 99 =
  6. 6.24 + 29 =
  7. 7.56 + 19 =
  8. 8.52 − 19 =
  9. 9.36 + 29 =
  10. 10.65 + 9 =
  11. 11.28 + 9 =
  12. 12.15 + 19 =
  13. 13.77 + 29 =
  14. 14.29 + 29 =
  15. 15.82 − 19 =
  16. 16.26 − 19 =
  17. 17.40 − 9 =
  18. 18.68 + 19 =
  19. 19.43 + 9 =
  20. 20.130 + 99 =
  21. 21.54 + 9 =
  22. 22.71 − 29 =
  23. 23.23 − 9 =
  24. 24.18 + 29 =
  25. 25.616 − 99 =
  26. 26.79 + 9 =
  27. 27.41 + 9 =
  28. 28.27 + 29 =
  29. 29.31 + 9 =
  30. 30.76 + 19 =
  31. 31.53 + 9 =
  32. 32.40 − 19 =
  33. 33.410 + 99 =
  34. 34.45 + 9 =
  35. 35.33 − 19 =
  36. 36.67 − 29 =
  37. 37.73 − 9 =
  38. 38.57 + 19 =
  39. 39.15 + 29 =
  40. 40.109 + 99 =

Answer key

  1. 77
  2. 70
  3. 562
  4. 107
  5. 675
  6. 53
  7. 75
  8. 33
  9. 65
  10. 74
  11. 37
  12. 34
  13. 106
  14. 58
  15. 63
  16. 7
  17. 31
  18. 87
  19. 52
  20. 229
  21. 63
  22. 42
  23. 14
  24. 47
  25. 517
  26. 88
  27. 50
  28. 56
  29. 40
  30. 95
  31. 62
  32. 21
  33. 509
  34. 54
  35. 14
  36. 38
  37. 64
  38. 76
  39. 44
  40. 208

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