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A radioactive substance has a half-life of 5 years. If the initial count rate is 80 counts per minute, what will the count rate be after 15 years? Use the smoke alarm context to keep Half-lives and the random nature of radioactive decay distinct from nearby atomic and nuclear radiation ideas.
- A.10 counts per minute (halflives and the random nature)
- B.20 counts per minute (halflives and the random nature)
- C.40 counts per minute (halflives and the random nature)
- D.30 counts per minute (halflives and the random nature)
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