Assuming exponential decay
amount = a e^(kt) where a is the initial amount, and t is number of years
.8 = 1 e^(250k(
ln .8 = ln e^(250k)
ln .8 = 250k
k = ln.8/250
after 600 years ?
amount = 1 e^(600ln.8/250) = .5853 or appr 58.5%
for half-life ?
.5 = e^(ln.8 t/250)
ln.5 = ln.8/250 t
t = 250ln .5/ln .8 = 776.6 years
If 80 percent of radioactive element is left after 250 years, then what percent remains after 600 years? What is the half life of the element?
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