The exponential growth function is
.
The half-life of carbon 14 is
years.
Hence, time period is
and 
Substitue all the values.
\

Apply natural logarithm on each side.
\



There,the decay constant is
.
A piece of charcoal is found to contain
of the carbon 14.
When did the tree die from which the charcoal came.
\
and
.
Susbtitute all the values in
.


Take natural logarithm on each side.
\


years.
Therefore, the tree die from which the charcoal came in
years ago.
The tree die from which the charcoal came in
years ago.