C14 is often used to tell the age of formerly living things.

C14 is often used to tell the age of formerly living things.C14 has a half-life of about 6000 years.Now,a cave is discovered with the remains of burned wood from a fire.The wood was found to be approximately 42000 years old.What percent of the original radioactive C14 remains in the charred wood?
谷歌翻译出来：C14经常被用来告诉岁以前生活的东西.C14的半衰期约6000年.现在,一个山洞里发现的遗骸从火中烧木头的.这种木材被发现是约42000年大的.多少百分比保持在原来的放射性C14烧焦的木头?