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## Homework Statement

Analysis of potassium and argon atoms in a moon rock sample shows that the ratio of the number of stable Ar-40 atoms to the number of radioactive K-40 atoms is 10.3.

Assume that all the Ar atoms were produces by the decay of K atoms, with a half-life of 1.25x10^ years.

(i)Calculate:

a) the fraction of the original K-40 atoms remaining in the rock

b) the number of half-lives that has elapsed

c) the age of the rock.

(ii) From the answers above, deduce the age of the solar system.

## Homework Equations

[tex]N=N_0e^{-\lambda t}[/tex]

## The Attempt at a Solution

Can someone guide me on how to start this?

"

*the number of*"

**stable**Ar-40 atoms to the number of radioactive K-40 atoms is 10.3.Now in the formula N=N_0exp(-[itex]\lambda t[/itex]) N is the no. of radioactive atoms at time t, So I am a bit lost.

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