(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

The technique known as potassium-argon dating is used to date old lava flows. The potassium isotope^{40}K has a 1.28 billion year half-life and is naturally present at very low levels.^{40}K decays by beta emission into^{40}Ar. Argon is a gas, and there is no argon in flowing lava because the gas escapes. Once the lava solidifies, any argon produced in the decay of^{40}K is trapped inside and cannot escape. A geologist brings you a piece of solidified lava in which you find the^{40}Ar/^{40}K ratio to be 0.12. What is the age of the rock?

2. Relevant equations

N=N_{0}(1/2)^{t/t[1/2]}

where N is the number of nuclei, N_{0}is the initial number of nuclei, t is time allowed to decay and t[1/2] is the half life.

3. The attempt at a solution

I actually do not know where to start with this one. I'm not sure how to apply the ratio given, and what variable I am even looking for, or if i'm even supposed to look at the relevant equation.

Could someone please point me in the right direction?

Thanks in advanced!

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# Homework Help: Finding the age of a rock

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