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August 20, 2014

August 20, 2014

Posted by **diane** on Wednesday, January 12, 2011 at 8:01am.

a certain element has a half life of 12 years. if there were 1000 milligrams originally, find the remaining amount after 20 years?

- math -
**drwls**, Wednesday, January 12, 2011 at 8:15am1000 mg*(1/2)^(20/12)

= 1000 mg*(1/2)^(5/3)

= 1000 mg*(1/2)^1.6667 = 315 mg

I used a hand calculator with a y^x key.

You can also use Google calculator.

http://www.google.com/search?q=1000*%281%2F2%29^%285%2F3%29&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a

- math -
**Jessica**, Monday, January 24, 2011 at 8:53pmRatios and Rates.

Questions: What is the ratio of gold protons to silver protons with gold being 79 and silver being 47?

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