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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 460 · 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. 1.236 + 99 =
  2. 2.42 − 29 =
  3. 3.71 − 19 =
  4. 4.26 + 29 =
  5. 5.38 + 19 =
  6. 6.81 − 9 =
  7. 7.408 − 99 =
  8. 8.102 − 29 =
  9. 9.85 − 29 =
  10. 10.833 − 99 =
  11. 11.50 + 19 =
  12. 12.303 − 99 =
  13. 13.638 + 99 =
  14. 14.97 − 19 =
  15. 15.74 + 19 =
  16. 16.26 − 9 =
  17. 17.64 + 9 =
  18. 18.48 − 29 =
  19. 19.86 − 29 =
  20. 20.20 + 19 =
  21. 21.28 + 29 =
  22. 22.31 + 19 =
  23. 23.22 + 19 =
  24. 24.47 − 29 =
  25. 25.60 − 29 =
  26. 26.77 + 19 =
  27. 27.465 + 99 =
  28. 28.53 − 9 =
  29. 29.42 + 9 =
  30. 30.12 − 9 =
  31. 31.564 − 99 =
  32. 32.96 − 29 =
  33. 33.61 − 19 =
  34. 34.48 + 29 =
  35. 35.239 − 99 =
  36. 36.26 + 19 =
  37. 37.58 + 9 =
  38. 38.40 − 9 =
  39. 39.28 + 9 =
  40. 40.428 + 99 =

Answer key

  1. 335
  2. 13
  3. 52
  4. 55
  5. 57
  6. 72
  7. 309
  8. 73
  9. 56
  10. 734
  11. 69
  12. 204
  13. 737
  14. 78
  15. 93
  16. 17
  17. 73
  18. 19
  19. 57
  20. 39
  21. 57
  22. 50
  23. 41
  24. 18
  25. 31
  26. 96
  27. 564
  28. 44
  29. 51
  30. 3
  31. 465
  32. 67
  33. 42
  34. 77
  35. 140
  36. 45
  37. 67
  38. 31
  39. 37
  40. 527

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