Every 4.5 billion years, half of the atoms in a sample of uranium-238 will undergo radioactive decay and become atoms of lead-206. suppose you lived in another planetary system around a faraway star and found meteorite that was originally made of uranium-238, but is now one-quarter uranium-238 and three quarters lead-206. what would be your best estimate of the planetary system?

The planetary system is 9 billion years old

Explanation:

In 4.5 billion years, the meteorite was half uranium and half lead. For this amount of uranium to be reduced by half again (reaching 1/4 uranium and 3/4 lead), another 4.5 billion years must have passed. Then, the planetary system should be 9 (2 x 4.5) billion years old.

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