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dedylja [7]
2 years ago
4

A rock contains 12.5% of its orignal K40 (half life = 704 million years). How old is the rock?

Biology
1 answer:
abruzzese [7]2 years ago
4 0
Half-life is the time needed for a radioactive material to decay 50% of its original mass. In this question, the rock K-40 left is 12.5% of its original weight. Then, the calculation to find the rock age should be:

final mass= (1/2)^(age/half life) * original mass
12.5% original mass= (1/2)^(age/704 years) * original mass
1/8= (1/2)^(age/704 years)
(1/2)^3= (1/2)^(age/704 years)
(age/704 years)= 3
age= 3 * 704 years= 2112 years
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