Rate of radioactive decay?

Question

Can someone please work through this problem with me:

For a first order reaction the rate R = −k N so the ratio of rates at two different times is given by R(t1)/R(t2) = N(t1)/N(t2).
For nuclear decay the rate is ofen is expressed in units of counts per unit of time.


A chemists determines that a sample of petrified wood is 5.00 X 103 years old. What is the rate of decay, in counts per minute per gram, of carbon-14 in the sample? The decay rate of carbon-14 in wood today is 13.6 counts per minute per gram, and the half life of carbon-14 is 5730 years.

Answer 1

6.7 counts per minute per gram.