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Concentration changes over time

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The radioisotope 198Au decays to 198Hg with a half-life of 2.69 days.
If a sample initially contains 9.10mg of 198Au, what mass of 198Au remains after 3.50 days?
Write your answer using three significant figures.
  • Your answer should be
  • an integer, like 6
  • a simplified proper fraction, like 3/5
  • a simplified improper fraction, like 7/4
  • a mixed number, like 1 3/4
  • an exact decimal, like 0.75
  • a multiple of pi, like 12 pi or 2/3 pi