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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?
 11 months ago
 11 months 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?
 11 months ago
 11 months 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 \(k\)
 11 months ago

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

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

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

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

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

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