Question

How much radioactive kind of europium will be left after 39 years if the half life is 13 years and you start with 1216 grams

Answer 1

`\textit{Amount for Exponential Decay using Half-Life} \\\\ A=P\left( (1)/(2) \right)^{(t)/(h)}\qquad \begin{cases} A=\textit{current amount}\\ P=\textit{initial amount}\dotfill &1216\\ t=\textit{elapsed time}\dotfill &39\\ h=\textit{half-life}\dotfill &13 \end{cases} \\\\\\ A=1216\left( (1)/(2) \right)^{(39)/(13)}\implies A=1216\left( (1)/(2) \right)^3\implies A=152`