Carbon-14 has a half-life of about 5,730 years. If a fossil sample initially contained 100. g of carbon-14, approximately how many grams remain after 17,190 years?
A50.0 g
B25.0 g
C12.5 g
D6.25 g
Explanation
📌 17,190 years ÷ 5,730 years per half-life = 3 half-lives. After each half-life, the remaining amount halves. So 100 g → 50 g (1st) → 25 g (2nd) → 12.5 g (3rd). General formula: remaining = initial × (1/2)ⁿ, where n is the number of half-lives elapsed. This is the basis of radiocarbon dating for fossils up to ~50,000 years old.
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