Almost all of naturally occurring uranium is 21$\J with
Chapter 41, Problem 41.85(choose chapter or problem)
Almost all of naturally occurring uranium is 21$\J with ahalf-life of 4.468 X 109yr. Most of the rest of naturaluranium is with a half-life of 7.04 X 108yr. Today asample contains 0.720% ^ U . (a) What was this percentage1.0 billion years ago? (b) What percentage of willremain 100 million years from now?
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