# Radiometric age dating of a moon rock sample

What is the formula to calculate the age of a moon rock sample? For example, how would I calculate the age of a moon rock sample knowing the number of grams of potassium-40 and argon-40 with a given half-life in a closed system assuming no argon-40 was present when the rock was formed?

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#### Solution Preview

The formula is

t = 1/k x ln (1+ D/P)

where

t = the age of the sample

D = number of atoms of the daughter isotope in the sample

P = number of atoms of the parent isotope in the sample

k = decay constant of the parent isotope

ln = natural logarithm

0.693/k = the half-life of K-40, which is 1.27 billion years. Given the number of grams, you can ...

#### Solution Summary

Radiometric age dating of a moon rock sample using K-40 and Ar-40.

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