The general equation for radioactive decay is; N = N₀e^(-λt) x - decay constant (λ) - rate of decay t- time N - amount remaining after t days , since we are calculating the half life, amount of time it takes for the substance to to be half its original value, its N₀/2 N₀ - amount initially present substituting the values N₀/2 = N₀e^(-0.081t) 0.5 = e^(-0.081t) ln (0.5) = -0.081t -0.693 = -0.081t t = 0.693 / 0.081 = 8.55 half life of substance is 8.55 days
