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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 484 · 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. 1.107 − 29 =
  2. 2.73 + 19 =
  3. 3.53 + 19 =
  4. 4.64 + 19 =
  5. 5.33 − 29 =
  6. 6.61 − 29 =
  7. 7.193 + 99 =
  8. 8.44 + 29 =
  9. 9.47 + 29 =
  10. 10.48 − 19 =
  11. 11.628 − 99 =
  12. 12.42 + 29 =
  13. 13.58 + 9 =
  14. 14.47 − 19 =
  15. 15.69 − 19 =
  16. 16.476 − 99 =
  17. 17.773 + 99 =
  18. 18.759 + 99 =
  19. 19.24 − 9 =
  20. 20.86 − 19 =
  21. 21.68 − 19 =
  22. 22.70 + 9 =
  23. 23.50 − 9 =
  24. 24.40 + 9 =
  25. 25.36 − 29 =
  26. 26.35 + 19 =
  27. 27.29 + 9 =
  28. 28.195 + 99 =
  29. 29.197 − 99 =
  30. 30.77 − 9 =
  31. 31.28 + 29 =
  32. 32.22 + 29 =
  33. 33.74 + 29 =
  34. 34.38 − 19 =
  35. 35.897 − 99 =
  36. 36.39 + 19 =
  37. 37.40 + 19 =
  38. 38.38 + 29 =
  39. 39.580 − 99 =
  40. 40.320 − 99 =

Answer key

  1. 78
  2. 92
  3. 72
  4. 83
  5. 4
  6. 32
  7. 292
  8. 73
  9. 76
  10. 29
  11. 529
  12. 71
  13. 67
  14. 28
  15. 50
  16. 377
  17. 872
  18. 858
  19. 15
  20. 67
  21. 49
  22. 79
  23. 41
  24. 49
  25. 7
  26. 54
  27. 38
  28. 294
  29. 98
  30. 68
  31. 57
  32. 51
  33. 103
  34. 19
  35. 798
  36. 58
  37. 59
  38. 67
  39. 481
  40. 221

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