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m_a_m_a [10]
3 years ago
7

A rock has 12.5 percent of its original amount of potassium-40 remaining in it; potassium-40 has a half-life of 1.25 billion yea

rs. How long ago was the rock formed?
a) 1.25 billion years ago

b) 2.5 billion years ago

c) 3.75 billion years ago

d) 5 billion years ago
Chemistry
2 answers:
igor_vitrenko [27]3 years ago
7 0
A rock has 12.5 percent of its original amount of potassium-40 remaining in it; potassium-40 has a half-life of 1.25 billion years. <span>3.75 billion years ago</span> was the <span>rock formed. the answer is letter C</span>
mylen [45]3 years ago
6 0

Answer:

the answer is b) 2.5 billion years.  if its half life is 1.25 billion years and there is only 25% of the element remaining, you would take 1.25 billion and multiply it by two to get 2.5 billion.

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