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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 257 · 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. 1.58 − 29 =
  2. 2.57 − 9 =
  3. 3.53 − 19 =
  4. 4.74 + 29 =
  5. 5.46 + 9 =
  6. 6.156 + 99 =
  7. 7.771 − 99 =
  8. 8.175 + 99 =
  9. 9.410 + 99 =
  10. 10.69 + 19 =
  11. 11.37 + 19 =
  12. 12.93 − 19 =
  13. 13.49 + 9 =
  14. 14.641 + 99 =
  15. 15.56 + 9 =
  16. 16.21 + 19 =
  17. 17.53 + 29 =
  18. 18.54 + 29 =
  19. 19.494 − 99 =
  20. 20.75 + 29 =
  21. 21.94 − 19 =
  22. 22.625 − 99 =
  23. 23.18 + 29 =
  24. 24.31 − 19 =
  25. 25.61 + 19 =
  26. 26.20 + 9 =
  27. 27.63 + 19 =
  28. 28.69 − 9 =
  29. 29.657 − 99 =
  30. 30.26 − 9 =
  31. 31.108 − 29 =
  32. 32.66 − 9 =
  33. 33.78 − 9 =
  34. 34.34 + 29 =
  35. 35.780 − 99 =
  36. 36.600 + 99 =
  37. 37.444 − 99 =
  38. 38.152 + 99 =
  39. 39.105 − 29 =
  40. 40.59 + 9 =

Answer key

  1. 29
  2. 48
  3. 34
  4. 103
  5. 55
  6. 255
  7. 672
  8. 274
  9. 509
  10. 88
  11. 56
  12. 74
  13. 58
  14. 740
  15. 65
  16. 40
  17. 82
  18. 83
  19. 395
  20. 104
  21. 75
  22. 526
  23. 47
  24. 12
  25. 80
  26. 29
  27. 82
  28. 60
  29. 558
  30. 17
  31. 79
  32. 57
  33. 69
  34. 63
  35. 681
  36. 699
  37. 345
  38. 251
  39. 76
  40. 68

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