Scientists found stone tool specimens in a cave in Africa. Using potassium-argon radiometric dating, they discovered that the tools contained 25 percent radioactive potassium-40. How old are the tools? (You must show your calculations to receive credit.) * The half-life for potassium-40 to argon-40 is 1.25 billion years.

Question

Biology

Kristopher Marquez

8 October, 11:53

Scientists found stone tool specimens in a cave in Africa. Using potassium-argon radiometric dating, they discovered that the tools contained 25 percent radioactive potassium-40. How old are the tools? (You must show your calculations to receive credit.) * The half-life for potassium-40 to argon-40 is 1.25 billion years.

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Zion Bass · Answer 1

The potassium remaining is 1/4 of the original, so two half lives have passed.

One half life = 1.25 billion years

Two half lives = 1.25 x 2 = 2.5 billion years

The tools are 2.5 billion years old.