A substance is decaying exponentially. Originally, there were 250 grams. After 1 hour, there were 200 grams. How many grams will there be after 5.3 hours? (Round to the nearest gram.) Solution N =No e^-kt or, ln(No/N) = kt or, ln(250/200) = k*1 or k =0.223/hrs So, at t=5.3 hrs N = 250e^-5.3*.223 or, N = 76.923 g.