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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 447 · 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. 1.69 − 9 =
  2. 2.181 + 99 =
  3. 3.277 + 99 =
  4. 4.60 + 29 =
  5. 5.74 − 29 =
  6. 6.74 + 19 =
  7. 7.363 + 99 =
  8. 8.79 − 19 =
  9. 9.36 + 19 =
  10. 10.59 − 19 =
  11. 11.25 + 19 =
  12. 12.50 − 29 =
  13. 13.457 + 99 =
  14. 14.27 + 19 =
  15. 15.766 + 99 =
  16. 16.76 + 9 =
  17. 17.21 − 9 =
  18. 18.53 − 9 =
  19. 19.25 + 9 =
  20. 20.289 + 99 =
  21. 21.30 + 9 =
  22. 22.89 − 19 =
  23. 23.86 − 9 =
  24. 24.75 + 29 =
  25. 25.155 + 99 =
  26. 26.566 + 99 =
  27. 27.70 − 19 =
  28. 28.14 − 9 =
  29. 29.72 + 29 =
  30. 30.819 − 99 =
  31. 31.33 − 19 =
  32. 32.818 − 99 =
  33. 33.74 + 9 =
  34. 34.64 − 9 =
  35. 35.151 + 99 =
  36. 36.14 + 9 =
  37. 37.545 + 99 =
  38. 38.33 + 9 =
  39. 39.22 + 19 =
  40. 40.31 + 19 =

Answer key

  1. 60
  2. 280
  3. 376
  4. 89
  5. 45
  6. 93
  7. 462
  8. 60
  9. 55
  10. 40
  11. 44
  12. 21
  13. 556
  14. 46
  15. 865
  16. 85
  17. 12
  18. 44
  19. 34
  20. 388
  21. 39
  22. 70
  23. 77
  24. 104
  25. 254
  26. 665
  27. 51
  28. 5
  29. 101
  30. 720
  31. 14
  32. 719
  33. 83
  34. 55
  35. 250
  36. 23
  37. 644
  38. 42
  39. 41
  40. 50

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