A researcher claims that an ancient scroll originated from Greek scholars in about 500 B.C. Its carbon-14 decay rate is 91 % of that found in living organisms. How old is the scroll? (The half-life of carbon-14 is 5730 yr) Solution Carbon-14 dating formula T = [ln(N f /N O )/(-0.693)] x T 1/2 Where Nf = Remaining carbon-14 % No = Initial carbon-14 % = 100% (constant always) T 1/2= Carbon-14 half-life (5730 years) Given remaining carbon-14 percentage is 91% Therefore T=[ln(91)/(100) / (-0.693)] x 5730 = 779.798 yrs Approximately 780 years .