Question 1206895
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Let x be the number half-lives in 30 years.  Then, since 250g decays to 150g in 30 years,<br>
{{{150=250(0.5)^x}}}
{{{(0.5)^x=0.6}}}
{{{xlog(0.5)=log(0.6)}}}
{{{x=log(0.6)/log(0.5)}}} = 0.7369656 to several decimal places<br>
The half life is then<br>
{{{30/0.7369656}}} = 40.71 to 2 decimal places<br>
ANSWER: 40.71 years<br>