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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 615 · 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. 1.87 − 19 =
  2. 2.75 + 9 =
  3. 3.482 − 99 =
  4. 4.626 − 99 =
  5. 5.216 + 99 =
  6. 6.32 − 29 =
  7. 7.35 + 19 =
  8. 8.50 − 29 =
  9. 9.66 + 9 =
  10. 10.42 + 9 =
  11. 11.26 − 19 =
  12. 12.364 − 99 =
  13. 13.764 + 99 =
  14. 14.598 − 99 =
  15. 15.274 − 99 =
  16. 16.736 + 99 =
  17. 17.54 + 9 =
  18. 18.19 + 9 =
  19. 19.34 − 29 =
  20. 20.60 + 19 =
  21. 21.36 − 19 =
  22. 22.538 + 99 =
  23. 23.383 − 99 =
  24. 24.276 + 99 =
  25. 25.726 + 99 =
  26. 26.633 + 99 =
  27. 27.96 − 29 =
  28. 28.73 + 9 =
  29. 29.66 + 29 =
  30. 30.16 + 19 =
  31. 31.41 − 29 =
  32. 32.53 − 29 =
  33. 33.74 + 19 =
  34. 34.55 + 9 =
  35. 35.65 + 9 =
  36. 36.18 + 29 =
  37. 37.86 − 29 =
  38. 38.17 + 19 =
  39. 39.20 + 19 =
  40. 40.80 − 9 =

Answer key

  1. 68
  2. 84
  3. 383
  4. 527
  5. 315
  6. 3
  7. 54
  8. 21
  9. 75
  10. 51
  11. 7
  12. 265
  13. 863
  14. 499
  15. 175
  16. 835
  17. 63
  18. 28
  19. 5
  20. 79
  21. 17
  22. 637
  23. 284
  24. 375
  25. 825
  26. 732
  27. 67
  28. 82
  29. 95
  30. 35
  31. 12
  32. 24
  33. 93
  34. 64
  35. 74
  36. 47
  37. 57
  38. 36
  39. 39
  40. 71

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