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4. What is the half-life of an element if a 500. gram sample decays to 62.5 grams in 639,000 years? 5. If there are 25.0 grams of a sample of thorium-232 left after 2.80 x 1010 years, how many grams were in the original sample? 6. How long will it take for 16 grams of Ra-226 to break down until only 1.0 grams … ................
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