Question 379009
Plutonium 239 is used as fuel for some nuclear reactors, and also as the
 fissionable material in atomic bombs.
 it has a half life of 24400 years. how long would it take 10 grams of
 plutonium 239 to decay to 1 gram?(round your answer to three significant digits)
:
The half life formula: Ao*2^(-t/h) = A
where
A = resulting amt after t yrs
Ao = initial amt
t = time in yrs
h = half-life of substance
:
10*2(-t/24400) = 1
Divide both sides by 10
2(-t/24400) = .1
Using nat logs
ln(2(-t/24400)) = ln(.1)
{{{-t/24400}}}ln(2) = ln(.1)
{{{-t/24400}}} = {{{ln(.1)/ln(2)}}}
Using a calc
{{{-t/24400}}} = -3.32193
Multiply both sides by -24400
t = 81,055.0456 years
:
:
Check solution on a calc; enter 10*2^(-81055/24400) results: 1.000