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A radioactive substance has a half-life of 5700 years. This means every 5700 years, the amount of substance is reduced to half of what it was at the beginning.
A sample initially contains 80g of the substance.
Write down how much remains after one half-life and after two half-lives.
After how many years will the amount of substance first fall below 20g?
A bone fragment is found to contain 10% of its original radioactive isotope.
Use the concept of half-lives to estimate its age, giving your answer to the nearest 1000 years.
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