# half life

• Sep 9th 2008, 05:21 PM
cwarzecha
half life
Find the half-life (in hours) of a radioactive substance that is reduced by 15 percent in 60 hours
• Sep 9th 2008, 05:30 PM
topsquark
Quote:

Originally Posted by cwarzecha
Find the half-life (in hours) of a radioactive substance that is reduced by 15 percent in 60 hours

Again
$A(t) = A_0 \left ( \frac{1}{2} \right ) ^{t/t_{1/2}}$

So
$\frac{A(t)}{A_0} = 0.15 = \left ( \frac{1}{2} \right ) ^{60/t_{1/2}}$
Solve for $t_{1/2}$.

-Dan