A radioactive sample contains 1280 g of nuclide with a half-life of 3 hours. How much remains after 9 hours?

Answer and explanation

Correct answer: B. 160 g

  1. Step 1: The number of half-lives is .
  2. Step 2: Remaining g.
Answer
160 g.
Why not the others: 213.333 g: the mass is divided by . 320 g: it halves one time too few. 80 g: it halves one time too many.

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