After 3 half-lives, what percentage of the original number of parent atoms is left? _______ (a number)
Question
After 3 half-lives, what percentage of the original number of parent atoms is left? _______ (a number)
Solution
A half-life is the time it takes for half of the atoms in a sample to decay.
- After one half-life, 50% of the original atoms remain.
- After two half-lives, 50% of the remaining 50% (or 25%) of the original atoms remain.
- After three half-lives, 50% of the remaining 25% (or 12.5%) of the original atoms remain.
So, after 3 half-lives, 12.5% of the original number of parent atoms is left.
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