Carbon–14 is a radioactive isotope that decays exponentially at a rate of 0.0124 percent a year. How many years will it take for carbon–14 to decay to 10 percent of its original amount? The equation for exponential decay is At = A0e–rt.
10%=1/10 1/10P=P(0.999876)^t divide both sides by P 1/10=0.999876^t take ln of both sides ln(1/10)=t (ln(0.999876)) divide both sides by (ln(0.999876)) ln(1/10)/(ln(0.999876))=t use calculator 18568.08=t about 18568 years
