A wooden object from a prehistoric site has a carbon-14 activity of 10 cpm compared to 40 cpm for new wood. If carbon-14 has a half-life of 5730 yr, what is the age of the wood?

The answer to your question is 11460 years

Explanation:

Data

Carbon-14 activity  10 cpm

half-life = 5730 yr

Real carbon-14 activity 40 cpm

Process

1.- Write a chart to solve this problem

                    Real carbon-14      40 cpm       Time  0 years

                    After a half-life      20 cpm        Time  5730 years

                    After a half-life      10 cpm        Time 5730 years

    Total time                                                            11460 years          

2.- Conclusion

The wooden object is 11460 years old.