x3_drummerchick
  • x3_drummerchick
How do i solve this!? Will give medals! Radium-221 has a half-life of 30 sec. How long will it take for 84% of a sample to decay? (Round your answer to the nearest whole number.)
Mathematics
  • Stacey Warren - Expert brainly.com
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SOLVED
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chestercat
  • chestercat
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x3_drummerchick
  • x3_drummerchick
@Nnesha
x3_drummerchick
  • x3_drummerchick
@Jhannybean
x3_drummerchick
  • x3_drummerchick
@dan815

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More answers

dan815
  • dan815
okay so basically
dan815
  • dan815
we keep losing 1/2 ever 30 seconds
x3_drummerchick
  • x3_drummerchick
i found the 'r' by doing ln2/30
dan815
  • dan815
wait i have to figure it out too
dan815
  • dan815
|dw:1443224796743:dw|
dan815
  • dan815
|dw:1443224894019:dw|
dan815
  • dan815
then we multiply 30*n to see how many seconds
x3_drummerchick
  • x3_drummerchick
im confused
dan815
  • dan815
okay let me see how to explain this
x3_drummerchick
  • x3_drummerchick
oohhh wait wait i think i know what you mean
x3_drummerchick
  • x3_drummerchick
you start with 1 mg
x3_drummerchick
  • x3_drummerchick
i mean, 1 "sample" of it, right?
dan815
  • dan815
yep
x3_drummerchick
  • x3_drummerchick
okay, and howd you get the (1/2)?
dan815
  • dan815
okay so forget like the 30 secs to begin with i mean remember it but we really wanna see how many half lives have passed we just know 1 half live is 30 seconds keep that in mind
x3_drummerchick
  • x3_drummerchick
Okay
dan815
  • dan815
basically like this, now you know that for every half life we multiply by a 1/2
x3_drummerchick
  • x3_drummerchick
okay
dan815
  • dan815
|dw:1443225179484:dw|
x3_drummerchick
  • x3_drummerchick
okay that makes sense
x3_drummerchick
  • x3_drummerchick
so how would we incorporate that into the formula?
x3_drummerchick
  • x3_drummerchick
|dw:1443225321392:dw|
dan815
  • dan815
okay
x3_drummerchick
  • x3_drummerchick
|dw:1443225534573:dw|
dan815
  • dan815
every 30 secs u want a new half lige so
dan815
  • dan815
life
x3_drummerchick
  • x3_drummerchick
okay
dan815
  • dan815
|dw:1443225561434:dw|
dan815
  • dan815
i believe this works
dan815
  • dan815
let me thing hmm
dan815
  • dan815
think
x3_drummerchick
  • x3_drummerchick
here is an example layout, but doesnr have answers, it confused me
1 Attachment
x3_drummerchick
  • x3_drummerchick
i dont know if that helps any
dan815
  • dan815
gimme a few mins, i am dealing with someone here
x3_drummerchick
  • x3_drummerchick
okay
dan815
  • dan815
yeah dont worry ill help u understand this stuff its pretty simple
x3_drummerchick
  • x3_drummerchick
okay thanks!
x3_drummerchick
  • x3_drummerchick
actually i think i figured it out!
dan815
  • dan815
waiitt okay
dan815
  • dan815
i want to show u something important first
dan815
  • dan815
are you there
x3_drummerchick
  • x3_drummerchick
crap, nvm i got it wrong
dan815
  • dan815
okay remember the (1/2)^n formula
x3_drummerchick
  • x3_drummerchick
yeah
dan815
  • dan815
now lets tweak that a little bit okay we know that for evert 30 secs we want it to be halved so
dan815
  • dan815
1*(1/2)^(t/30)
dan815
  • dan815
now u see every 30 secs we would exactly half it
dan815
  • dan815
the equation they give u is this just in disguise
x3_drummerchick
  • x3_drummerchick
that makes sense
dan815
  • dan815
like for example
dan815
  • dan815
if we apply e^ln(x) = x e and ln cancel out right
dan815
  • dan815
lets apply to that equation we know has to be right
x3_drummerchick
  • x3_drummerchick
okay
dan815
  • dan815
e^ln((1/2)^(t/30))
dan815
  • dan815
do you know your ln rules like ln(x^3)= 3 ln x the power multiples
x3_drummerchick
  • x3_drummerchick
oh wait, dont you bring it to the rfont of the ln?
x3_drummerchick
  • x3_drummerchick
front *
dan815
  • dan815
|dw:1443226339275:dw|
dan815
  • dan815
with a little bit of manipulation we see that the equation is exactly reuivalent
dan815
  • dan815
equivalent
dan815
  • dan815
there is only 1 rule im applying here over and over
dan815
  • dan815
|dw:1443226451939:dw|
x3_drummerchick
  • x3_drummerchick
yes i do remember those
dan815
  • dan815
okay go ahead fill it all in now
x3_drummerchick
  • x3_drummerchick
|dw:1443226609625:dw|
dan815
  • dan815
yes that is correct
dan815
  • dan815
http://prntscr.com/8kirao
x3_drummerchick
  • x3_drummerchick
i got 79.33, is that right?
x3_drummerchick
  • x3_drummerchick
seconds
dan815
  • dan815
i am not using a calculator make sure u round it to the 10th
x3_drummerchick
  • x3_drummerchick
its correct :) thank you again so much, youre awesome!
dan815
  • dan815
okay you're welcome :)

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