Answer :
The number of half-lives that has elapsed when 3 atoms of the radioactive substance remains is 6 (Option C)
Data obtained from the question
- Half-life (t½) = 500 million years
- Original amount (N₀) = 192 atoms
- Amount remaining (N) = 3 atoms
- Number of half-lives (n) =?
How to determine the number of half-lives
2ⁿ = N₀ / N
2ⁿ = 192 / 3
2ⁿ = 64
2ⁿ = 2⁶
n = 6
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