A Paleontologist Estimates That When a Particular Rock Formed, It

question 19

Multiple Choice

A paleontologist estimates that when a particular rock formed, it contained 12 mg of the radioactive isotope potassium-40, which has a half-life of 1.25 billion years. The rock now contains 3 mg of the isotope. About how old is the rock?

• A) 2.5 billion years
• B) 5.0 billion years
• C) 1.25 billion years
• D) 0.3 billion years
• E) 0.4 billion years

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