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openstudyhelpplease
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A certain radioactive element decays according to N=No e ^kt. If 50% of the original element sample remains after 9 days, what is the decay rate?
 one year ago
 one year ago
openstudyhelpplease Group Title
A certain radioactive element decays according to N=No e ^kt. If 50% of the original element sample remains after 9 days, what is the decay rate?
 one year ago
 one year ago

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satellite73 Group TitleBest ResponseYou've already chosen the best response.2
you know if \(t=9\) you have half of what you started with set \[e^{9k}=.5\] and solve for \(k\)
 one year ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.2
you got this? solve in two steps only
 one year ago

openstudyhelpplease Group TitleBest ResponseYou've already chosen the best response.0
how do you solve for k?
 one year ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.2
1) write in equivalent logarithmic form (take the log) 2) divide by 9
 one year ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.2
\[e^{9k}=.5\iff 9k=\ln(.5)\iff k=\frac{\ln(.5)}{9}\]
 one year ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.2
then if you want a decimal, use a calculator
 one year ago

openstudyhelpplease Group TitleBest ResponseYou've already chosen the best response.0
i have no idea what that means haha. so is it: k= .1831?
 one year ago

openstudyhelpplease Group TitleBest ResponseYou've already chosen the best response.0
wait is ln the button on the calculator for e?
 one year ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.2
http://www.wolframalpha.com/input/?i=ln%28.5%29%2F9 usually \(ln\) is the button and \(e\) requires the shift key
 one year ago

openstudyhelpplease Group TitleBest ResponseYou've already chosen the best response.0
ok, so i have to use the shift key right? i tried doing e ^.5 which was 1.64 and then divide that by 9 which was .1831
 one year ago

openstudyhelpplease Group TitleBest ResponseYou've already chosen the best response.0
oh, the link helped. sorry we didn't learn this yet so I have no idea what im talking about
 one year ago

openstudyhelpplease Group TitleBest ResponseYou've already chosen the best response.0
so the rate is k= 7.7 x 10 ^2
 one year ago
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