# Chapter 33 - Think and Solve: 36

23,000 years.

#### Work Step by Step

After one half-life, we are down to one-half the original amount. After two half-lives, we are down to one-quarter the original amount. After three half-lives, we are down to one-eighth the original amount. After four half-lives, we are down to one-sixteenth the original amount. The intensity decreased by a factor of 16.7 (from 100 percent to 6 percent). This is a little over 4 half-life periods. So the wood is a little over (4)(5730 years) old, roughly 23,000 years.

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