math
posted by diane .
how to compute this problem?
a certain element has a half life of 12 years. if there were 1000 milligrams originally, find the remaining amount after 20 years?

1000 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=utf8&oe=utf8&aq=t&rls=org.mozilla:enUS:official&client=firefoxa 
Ratios and Rates.
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