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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 720 · 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. 1.503 − 99 =
  2. 2.18 − 9 =
  3. 3.85 − 29 =
  4. 4.206 − 99 =
  5. 5.441 + 99 =
  6. 6.26 − 9 =
  7. 7.41 + 19 =
  8. 8.602 − 99 =
  9. 9.49 + 29 =
  10. 10.159 + 99 =
  11. 11.13 − 9 =
  12. 12.29 + 19 =
  13. 13.60 − 29 =
  14. 14.19 + 29 =
  15. 15.53 − 9 =
  16. 16.213 − 99 =
  17. 17.230 − 99 =
  18. 18.23 + 29 =
  19. 19.14 + 9 =
  20. 20.332 + 99 =
  21. 21.31 − 19 =
  22. 22.66 − 9 =
  23. 23.44 − 9 =
  24. 24.78 + 29 =
  25. 25.86 − 29 =
  26. 26.77 + 19 =
  27. 27.52 + 19 =
  28. 28.69 + 9 =
  29. 29.64 − 29 =
  30. 30.40 + 29 =
  31. 31.82 − 19 =
  32. 32.48 − 29 =
  33. 33.43 + 29 =
  34. 34.64 + 9 =
  35. 35.70 + 19 =
  36. 36.27 − 9 =
  37. 37.24 + 29 =
  38. 38.74 + 19 =
  39. 39.74 + 29 =
  40. 40.71 + 19 =

Answer key

  1. 404
  2. 9
  3. 56
  4. 107
  5. 540
  6. 17
  7. 60
  8. 503
  9. 78
  10. 258
  11. 4
  12. 48
  13. 31
  14. 48
  15. 44
  16. 114
  17. 131
  18. 52
  19. 23
  20. 431
  21. 12
  22. 57
  23. 35
  24. 107
  25. 57
  26. 96
  27. 71
  28. 78
  29. 35
  30. 69
  31. 63
  32. 19
  33. 72
  34. 73
  35. 89
  36. 18
  37. 53
  38. 93
  39. 103
  40. 90

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