The half-life of a certain substance is 16 years. How long will it take for a sample of this substance to decay to 77% of the original amount?

Answer 1

.5 = e^16t

ln.5 = 16t

t = ln.5/16 = -4.33% decay rate per year

.77 = e^-.0433t

ln.77 = -.0433t

t = ln.77/-.0433 = 6.036 years to decay to 77% of its original amount