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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 599 · 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. 1.79 − 29 =
  2. 2.84 − 29 =
  3. 3.71 + 9 =
  4. 4.83 − 29 =
  5. 5.564 − 99 =
  6. 6.38 − 9 =
  7. 7.73 − 19 =
  8. 8.49 − 29 =
  9. 9.76 + 9 =
  10. 10.52 − 19 =
  11. 11.58 + 9 =
  12. 12.58 − 9 =
  13. 13.42 + 19 =
  14. 14.53 − 9 =
  15. 15.286 − 99 =
  16. 16.60 + 9 =
  17. 17.23 − 9 =
  18. 18.58 + 29 =
  19. 19.729 + 99 =
  20. 20.181 − 99 =
  21. 21.295 − 99 =
  22. 22.26 + 19 =
  23. 23.260 + 99 =
  24. 24.32 + 9 =
  25. 25.79 + 9 =
  26. 26.354 − 99 =
  27. 27.13 − 9 =
  28. 28.24 + 9 =
  29. 29.65 − 29 =
  30. 30.45 − 19 =
  31. 31.61 + 19 =
  32. 32.43 + 29 =
  33. 33.109 − 29 =
  34. 34.312 − 99 =
  35. 35.39 − 9 =
  36. 36.17 + 29 =
  37. 37.429 − 99 =
  38. 38.92 − 19 =
  39. 39.56 + 19 =
  40. 40.57 + 29 =

Answer key

  1. 50
  2. 55
  3. 80
  4. 54
  5. 465
  6. 29
  7. 54
  8. 20
  9. 85
  10. 33
  11. 67
  12. 49
  13. 61
  14. 44
  15. 187
  16. 69
  17. 14
  18. 87
  19. 828
  20. 82
  21. 196
  22. 45
  23. 359
  24. 41
  25. 88
  26. 255
  27. 4
  28. 33
  29. 36
  30. 26
  31. 80
  32. 72
  33. 80
  34. 213
  35. 30
  36. 46
  37. 330
  38. 73
  39. 75
  40. 86

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