5. the half-life of a certain radioactive material is 78 hours. an initial amount of the material has a mass of 790 kg. write an exponential function that models the decay of this material. find how much radioactive material remains after 18 hours. round your answer to the nearest thousandth.,

The half life is 78 hours and the amount after 78 hours is 395 kg hence time constant is 395 = 790 * e^(p*78) By taking 790 common and natural log on both side ln (395 / 790) = (p*78) -0.6931 = 78*p -0.0088 = p (or -0.88%) Material left after 18 hours is A(18) = 790 * e^(-0.0088*18) A = 673.301 kg

Ithink the answer is c