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Half-life is 5.27 years; 21 / 5.27 = 3.99, or almos 4 half-lives; (1/2)4 = 1/16.

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Q: Approximately what fraction of an original Co-60 sample remains after 21 years?
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Related questions

After three half-lives what fraction of a radioactive sample remains?

1/8 of the original amount remains.


What fraction of an original sample of a radio isotope remains after 3 half-life periods?

One eighth remains.


What fraction of an original 20.00gram sample of nitrogen-16 remains unchanged after 36.0 seconds?

2


What is the significance of a half life of a radioisotope?

It tells what fraction of a radioactive sample remains after a certain length of time.


Why After three half-lives what fraction of a radioactive sample remains?

After three half-lives, only 1/8 (or 12.5%) of the original radioactive sample remains. This is because each half-life reduces the amount of radioactive material by half, so after three half-lives, you would have (1/2) * (1/2) * (1/2) = 1/8 of the original sample remaining.


How much of a sample of radioisotope remains after one half-life?

After one half-life, approximately 50% of the original sample of radioisotope remains. This means that half of the original radioisotope has decayed into a stable form.


What fraction of a sample remains after three half lives?

An eighth remains.


What percentage of a radioactive sample remains after 5 half-lives?

After 5 half-lives, 3.125% (or 1/2^5) of a radioactive sample remains. Each half-life reduces the sample by half, so after 5 half-lives, there is only a small fraction of the original sample remaining.


What fraction of a sample of N 16 remains undecayed after 43.2 seconds?

1.5% remains after 43.2 seconds.


What is the fraction of a sample of tritium that remains undecayed after fifty years?

After 50 years, approximately 50% of tritium will remain undecayed in a sample. Tritium has a half-life of about 12.3 years, which means that the amount of undecayed tritium decreases by half every 12.3 years.


Which fraction of an original 20.00-gram sample of nitrogen-16 remains unchanged after 36.0 seconds?

Nitrogen-16 has a half-life of about 7.13 seconds. After 36.0 seconds, there would be 3 half-lives. Therefore, 1/2 * 1/2 * 1/2 = 1/8 of the original sample remains unchanged.


What fraction of a radioactive sample remains after three half - life?

It is 1/8 .