Im having trouble answering this question. How long it takes for 80% of the carbon-14 to decay in an animal after it has died. Carbon decays rate 0.012% per year. So, my understanding is, -(R = 0.00012 yr-1, t=1 yr) R=Ro exp (-λt) 0.00012=Ro exp(-λ(1)) ---- (1) -No = 0.8, No=λRo Ro=0.8/λ ------ (2) To find λ, (2) into (1) 0.00012=0.8/λ exp(-λ(1)) ∴ λ = 8.8 yrs-1 Now im stuck which equation i have to use to find the year? Are my assumption above is correct?