How many years old is a fossilized tree if it contains 25% of its original carbon-14

I appreciate everyones help here. Thanks

Try this site: http://science.howstuffworks.com/environ…

The half-life of carbon-14 is about 5700 years. So if a fossil contains 25% of its carbon-14, it has gone through two half-lives (first half life gets rid of half, leaving 50%, second half-life gets rid of half of the 50%, leaving 25%). So, the fossil is 2x5700 years (give or take) old.

why, did you find one in your backyard? Yankees.