Question 688703
Radioactive strontium-90 is used in nuclear reactors and decays according to A=Pe^-0.0248t
 where A is the amount remaining after t years.
 Find the time required for strontium-90 to decay to 1/10 of the quantity present now?
:
Let the initial amt (P) = 1; A = .1
{{{1*e^(-.0248t) = .1}}}
natural log of e = 1, therefore we can write it
-.0248t = ln(.1)
t = {{{ln(.1)/(-.0248)}}}; use a calc
t ~ 93 years