Posted by Jillian on Wednesday, August 22, 2012 at 9:28am.
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.

Calculuc  drwls, Wednesday, August 22, 2012 at 9:33am
e^(0.023t) = 0.5
Take natural log of both sides.
0.023 t = 0.6932
t = 30 years

Calculuc  Reiny, Wednesday, August 22, 2012 at 9:39am
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!!!
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