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The number of ^238 U atoms in an ancient...

The number of `^238 U` atoms in an ancient rock equals the number of `^206 Pb` atoms. The half-life of decay of `^238 U` is `4.5 xx 10^9 y`. Estimate the age of the rock assuming that all the `^206 Pb` atoms are formed from the decay of `^238 U`.

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The correct Answer is:
`[4.5 xx 10^(9)y` old]
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