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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 900 · 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. 1.128 + 99 =
  2. 2.61 − 29 =
  3. 3.72 − 19 =
  4. 4.859 − 99 =
  5. 5.41 − 9 =
  6. 6.241 + 99 =
  7. 7.17 − 9 =
  8. 8.44 − 19 =
  9. 9.21 + 9 =
  10. 10.66 − 9 =
  11. 11.72 + 19 =
  12. 12.598 + 99 =
  13. 13.38 − 19 =
  14. 14.13 + 29 =
  15. 15.59 + 19 =
  16. 16.17 + 19 =
  17. 17.77 + 9 =
  18. 18.79 − 9 =
  19. 19.69 + 9 =
  20. 20.14 + 9 =
  21. 21.27 + 9 =
  22. 22.46 − 29 =
  23. 23.679 + 99 =
  24. 24.22 + 9 =
  25. 25.34 − 29 =
  26. 26.23 + 9 =
  27. 27.737 + 99 =
  28. 28.709 − 99 =
  29. 29.501 + 99 =
  30. 30.39 − 29 =
  31. 31.409 + 99 =
  32. 32.15 + 19 =
  33. 33.35 − 29 =
  34. 34.52 − 19 =
  35. 35.39 + 29 =
  36. 36.38 + 9 =
  37. 37.97 − 29 =
  38. 38.93 − 29 =
  39. 39.208 + 99 =
  40. 40.13 − 9 =

Answer key

  1. 227
  2. 32
  3. 53
  4. 760
  5. 32
  6. 340
  7. 8
  8. 25
  9. 30
  10. 57
  11. 91
  12. 697
  13. 19
  14. 42
  15. 78
  16. 36
  17. 86
  18. 70
  19. 78
  20. 23
  21. 36
  22. 17
  23. 778
  24. 31
  25. 5
  26. 32
  27. 836
  28. 610
  29. 600
  30. 10
  31. 508
  32. 34
  33. 6
  34. 33
  35. 68
  36. 47
  37. 68
  38. 64
  39. 307
  40. 4

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