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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 854 · 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. 1.50 − 29 =
  2. 2.104 − 29 =
  3. 3.27 + 9 =
  4. 4.29 + 29 =
  5. 5.79 + 9 =
  6. 6.163 − 99 =
  7. 7.75 + 9 =
  8. 8.550 + 99 =
  9. 9.15 − 9 =
  10. 10.488 + 99 =
  11. 11.26 + 19 =
  12. 12.325 − 99 =
  13. 13.49 − 9 =
  14. 14.73 − 29 =
  15. 15.510 + 99 =
  16. 16.41 − 19 =
  17. 17.39 + 19 =
  18. 18.341 − 99 =
  19. 19.63 − 29 =
  20. 20.405 + 99 =
  21. 21.41 − 9 =
  22. 22.32 − 9 =
  23. 23.80 + 29 =
  24. 24.404 + 99 =
  25. 25.31 + 29 =
  26. 26.34 + 9 =
  27. 27.99 − 19 =
  28. 28.31 − 9 =
  29. 29.24 − 19 =
  30. 30.295 − 99 =
  31. 31.75 − 9 =
  32. 32.201 + 99 =
  33. 33.83 − 29 =
  34. 34.17 − 9 =
  35. 35.71 − 29 =
  36. 36.76 + 29 =
  37. 37.27 + 29 =
  38. 38.73 + 29 =
  39. 39.68 + 9 =
  40. 40.402 + 99 =

Answer key

  1. 21
  2. 75
  3. 36
  4. 58
  5. 88
  6. 64
  7. 84
  8. 649
  9. 6
  10. 587
  11. 45
  12. 226
  13. 40
  14. 44
  15. 609
  16. 22
  17. 58
  18. 242
  19. 34
  20. 504
  21. 32
  22. 23
  23. 109
  24. 503
  25. 60
  26. 43
  27. 80
  28. 22
  29. 5
  30. 196
  31. 66
  32. 300
  33. 54
  34. 8
  35. 42
  36. 105
  37. 56
  38. 102
  39. 77
  40. 501

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