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The half-life of radon-$222$ is $3.8$ days. if a sample contains $4.2$ grams, how much will remain in the sample after $15.2$ days?

I've tried solving it written out, but I keep getting the wrong answer.

an4s
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Blue Note
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    You should post what you have done so far so that others can help you fix it. – an4s Jun 14 '18 at 23:11
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    Check wikipedia entry on half-life. https://en.wikipedia.org/wiki/Half-life If you still have trouble, come here and update your question with specific details. – user625 Jun 14 '18 at 23:16

1 Answers1

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Hint:

Use the equation $$N(t)=N_0e^{-\lambda t}$$ and $$\lambda=\frac{\ln2}{t_{\frac12}}$$ Half life time $t_{\frac12}=3.8$

$N_0=4.2$

Key Flex
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