Assertion: plutonium's life | /r/HasProperty | about 4.47 billion years
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Source sentences:
text: So the half-life of U-238 is about 4.47 billion years, and the half-life of U-235 is about 7.4 million years.
text: The half-life of uranium-238 is about 4.47 billion years and that of uranium-235 is 704 million years, making them useful in dating the age of the Earth.