Calculuc
posted by Jillian .
How do you set up this problem?
The decay constant for the radioactive element cesium 137 is .023 when time is measured in years. Find its halflife.

e^(0.023t) = 0.5
Take natural log of both sides.
0.023 t = 0.6932
t = 30 years 
If you are using the standard decay function equation
amount = initial amount e^kt, where k = .023 then
.5 = e^ .023t
.023t = ln .5
t = ln .5/.023 = 30.14 years
check: pick 500 grams
amount = 500 e^(.023(30.14))
= 500 e^ .69314..
= 250
YUP!!!