Homework Help: math

Posted by mike on Monday, March 30, 2009 at 1:16am.

if the rate for radioactive decay for a substance is r=-.0063 and time is being measured in days how do you find the half-life of the substance to the nearest hour?

math - Damon, Monday, March 30, 2009 at 3:35am
Do you mean
A(t) = Ao e^-(.0063 t) ????
If so then
1 = 2 e^-(.0063 t)
.5 = e^-(.0063 t)
ln .5 = -(.0063 t)
-.69315 = -(.0063 t)
t = 110.02 days which is about 110 days and one hour

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