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A radioactive substance of mass 768g has a half life of 3 years. After how many years ...

A radioactive substance of mass 768g has a half life of 3 years. After how many years does this substance leave only 6g undecayed?
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  • A 21
  • B 18
  • C 15
  • D 12
Correct Answer: Option A
Explanation:
\(768 \to 384 \to 192 \to 96 \to 48 \to 24 \to 12 \to 6\)
7 x 3 = 21yrs

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