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Choking Victim
September 26th, 2008, 03:24 PM
I realize this is probably frowned upon, but I really am stumped. While doing work for one of my AP classes I came across this question:


In a tree or other living organism, the amount of carbon-14 is quite low. In fact, the number of decays is only about 15.3 per minute. The rate remains constant while the tree is alive because the carbon-14 is being replaced in the tree through respiration. When the tree dies, the rate slowly decreases according to the half-life of carbon-14. Suppose a piece of fossil tree is analyzed and is found to be disintegrating at a rate of about 3.8 disintegrations per minute. About how old is this fossil? Show your work!!The half-life of Carbon-14 is 5,730 years.

I've searched on google, usually some of the questions teachers give out are from worksheets used nation-wide by most teachers, but I haven't found an answer sheet or anything to help me out. I understand most half-life problems, but the wording on this just throws me off. If anyone has anything to contribute to help me solve it, then please post. Thanks for your help.

Keep it serious please, I need help.

Edit: 15.3 / 2 = 7.65
7.65 / 2 = 3.825
That makes two half-lifes.
5730 x 2 = 11460 years.

I believe that's the answer, unless anyone thinks otherwise.