teller
  • teller
Can someone please help me ? The half-life of a radioactive isotope is the time it takes for a quantity of the isotope to be reduced to half its initial mass. Starting with 165 grams of a radioactive isotope, how much will be left after 3 half-lives?Use the calculator provided and round your answer to the nearest gram.
Algebra
  • Stacey Warren - Expert brainly.com
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SOLVED
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katieb
  • katieb
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anonymous
  • anonymous
\[A=A_0\cdot \left( \frac{ 1 }{ 2 } \right)^k\]where \(A_0\) is the initial amount \(A\) is the amount remaining after k half-lives and k is the number of half-lives
teller
  • teller
So 165=3*(1/2)^k?
anonymous
  • anonymous
no... A = 165*(1/2)^3

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More answers

teller
  • teller
165/8?
anonymous
  • anonymous
yep
teller
  • teller
but it has to be rounded to the nearest gram how do I do that? It can't be in fraction form.
anonymous
  • anonymous
divide and see what you get... the problem says to use the calculator provided but any calculator will work... or you can use long division
teller
  • teller
divide it by what do I divide 165 by 8?
anonymous
  • anonymous
yes, that is another way to represent 165/8
teller
  • teller
I got 20.625 is that right?
anonymous
  • anonymous
does that make sense to you? what is 20 * 8?
teller
  • teller
160
anonymous
  • anonymous
so let's rewrite: \[\frac{ 20\cdot 8 }{ 8}+\frac{ 5 }{ 8 }=\frac{ 160 }{ 8 }+\frac{ 5 }{ 8 }=\frac{ 165 }{8}\]and 5/8 is less than 1 but more than 1/2 = .5, correct?
anonymous
  • anonymous
so final answer, rounded to the nearest gram?
teller
  • teller
I'm confused at what I'm supposed to be rounding...
anonymous
  • anonymous
20.625
teller
  • teller
But how do I do that I already did that and I gave you the answer but you never told me if it was right.
teller
  • teller
I got that but how do I round that?
anonymous
  • anonymous
20.625 is not rounded to the nearest gram... 20.625 grams is the exact answer but they want the answer rounded to the nearest gram. which is closer to 20.625... 20 or 21?
teller
  • teller
20
teller
  • teller
no wait 21
anonymous
  • anonymous
there you go!
teller
  • teller
so 20.621?
anonymous
  • anonymous
?
teller
  • teller
you said 21 so 20.621
anonymous
  • anonymous
no... to the nearest gram... no numbers after the decimal!!!
teller
  • teller
oh okay thank you
teller
  • teller
Mind helping me with another one?
anonymous
  • anonymous
i would but i'm heading out. going for a bike ride. good luck!
teller
  • teller
Alright thanks

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