Lead-202 has a half-life of 53,000 years. How long will it take for 15/16 of a sample of lead-202 to decay?

If 15/16 of the sample decays, 1/16 remains. Four half-lives reduce the sample to 1/16, since (1/2)^4 = 1/16. Four half-lives take 4 × 53,000 = 212,000 years, so the answer is C, 212,000 years.

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