A radioactive sample has a half-life of 5 days. Its mass of the radioactive nuclide is 80 g. How much remains after 15 days?

Answer and explanation

Correct answer: D. 10 g

  1. Step 1: The number of half-lives is .
  2. Step 2: Remaining mass g.
Answer
10 g.
Why not the others: 13.333 g: it divides by rather than halving times. 20 g: it halves one time too few. 5 g: it halves one time too many.

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