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A pure sample of ⁶⁶₂₉Cu is taken, and after 15 minutes, (7)/(8) of it has transformed into Zn. What is the half-life of this nuclide?
- 15 minutes
- 10 minutes
- 7(1)/(2) minutes
- 5 minutes
Correct answer: 5 minutes
Solution
If 7/8 has transformed, 1/8 remains = (1/2)^3, so 3 half-lives elapsed in 15 minutes. Half-life = 15/3 = 5 minutes.
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