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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 905 · 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. 1.34 − 29 =
  2. 2.155 − 99 =
  3. 3.36 + 19 =
  4. 4.77 + 9 =
  5. 5.74 − 9 =
  6. 6.45 + 9 =
  7. 7.109 − 29 =
  8. 8.234 + 99 =
  9. 9.50 + 29 =
  10. 10.19 + 9 =
  11. 11.71 − 29 =
  12. 12.505 − 99 =
  13. 13.68 − 19 =
  14. 14.64 + 9 =
  15. 15.70 − 9 =
  16. 16.77 − 9 =
  17. 17.78 + 19 =
  18. 18.36 + 29 =
  19. 19.33 + 29 =
  20. 20.24 − 19 =
  21. 21.780 − 99 =
  22. 22.71 − 9 =
  23. 23.65 + 29 =
  24. 24.341 − 99 =
  25. 25.35 + 9 =
  26. 26.740 − 99 =
  27. 27.20 − 9 =
  28. 28.44 − 29 =
  29. 29.66 + 29 =
  30. 30.273 − 99 =
  31. 31.74 + 29 =
  32. 32.565 − 99 =
  33. 33.47 + 9 =
  34. 34.24 + 19 =
  35. 35.55 + 9 =
  36. 36.42 + 19 =
  37. 37.674 − 99 =
  38. 38.52 + 29 =
  39. 39.372 − 99 =
  40. 40.29 + 29 =

Answer key

  1. 5
  2. 56
  3. 55
  4. 86
  5. 65
  6. 54
  7. 80
  8. 333
  9. 79
  10. 28
  11. 42
  12. 406
  13. 49
  14. 73
  15. 61
  16. 68
  17. 97
  18. 65
  19. 62
  20. 5
  21. 681
  22. 62
  23. 94
  24. 242
  25. 44
  26. 641
  27. 11
  28. 15
  29. 95
  30. 174
  31. 103
  32. 466
  33. 56
  34. 43
  35. 64
  36. 61
  37. 575
  38. 81
  39. 273
  40. 58

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