<p>Here is the question involving radioactive decay in 1998 exam:
54. A sample of radioactive waste has a half-life of 10 years and an activity level of 2 curies. After how many years will the activity level of this sample be 0.25 curie?
(A) 10 years
(B) 20 years
(C) 30 years
(D) 40 years
(E) 80 years
I don’t think there will be many questions like this…but it helps to know. So does anyone know how to solve this? Knowing the answer doesn’t help me much. And when I google it…there is an e symbol I know has something to do with log…that I haven’t learn about.</p>
<p>^ (C)
10charsssss</p>
<p>K aquamarina- First step- divide 2 in half until you get to .25
2/2=1
1/2=.5
.5/2-.25, which is what you were looking for. </p>
<p>Now, since you divided 2 in half 3 times, it took 3 half lives. So 3 * 10 = 30, giving you the answer (C).</p>
<p>Hope that makes sense.</p>
<p>And the log would not help at all for this simple of a problem, and besides that, we can’t use calculators.</p>
<p>OH, thanks a lot puggly123!!!
Your explanation is muuuuch better than the equations they give me in google which involves exponents and e.</p>
<p>Ya, if we even have half-lives on this test then they will be very simple like that problem. No logs or e needed.</p>
<p>What prep book do you use?
5 Steps to a 5 never mentioned this :(</p>
<p>Neither did the REA or PR. And I agree. I hope the PR are alot more like the actual test than the REA.</p>
<p>im just rereading PR for the test tmrw
i have an ib history test too, so idk. im kinda freakin out about both right now.</p>
<p>aquamarina- did you use 5 steps to a 5 only? I have that one, I’d say it’s pretty bad. I used Princeton Review 2008 mostly.<br>
The practice tests in it are pretty easy, so I agree APFreak. Just got 90/100 on MC :-)</p>
<p>I hope the 1998 MC is similar to the exam tomorrow because I am going over it now. But it’s hard to to tell since it’s over 10 years. I am sure there has been some changes. But oh well, that’s better than nothing.
I am also going over the practice exam, and so far it’s harder than the 1998. I am surviving though.
OK, so does any one of you planning to have a good sleep night or will cram until like 11.
I don’t know. People say you should have a good rest before the exam. But won’t cramming help you better?</p>
<p>Oh yeah, I used only 5 Steps to a 5…Shouldn’t though…too late now.</p>
<p>I’m cramming lol</p>
<p>how realistic are the princeton review practice tests? they seem too easy to me. o_o</p>
<p>^I’m almost certain that it is easier than the real thing, especially compared to the 2003 release/audit.</p>
<p>And yeah, I have the 2003 release if anyone wants.</p>
<p>I feel like the PR practice tests are too easy too… 
I just took one today and it took me like half an hour and I got like 87/100. Yeahh, my teacher gave us a practice test and I got a 60/100.</p>
<p>& I’m going to review the rest of the labs sections, the vocab, and then do the second practice test and probably go to bed around 10?</p>
<p><a href=“https://docs.google.com/fileview?id=0B8tIZRtqagGWMjQyNjhjMzgtNzJmZi00YzIyLWE5ODItNTJmMTY5MTM4NTNk&hl=en[/url]”>https://docs.google.com/fileview?id=0B8tIZRtqagGWMjQyNjhjMzgtNzJmZi00YzIyLWE5ODItNTJmMTY5MTM4NTNk&hl=en</a></p>
<p>2003 (i think) release</p>
<p>pity. here i was thinking i was all set for a 5 ):
hey do you think a 71% on the MC [include .25 deductions and all that good stuff] for the 2008 audit and an average of 6-7/10 on each of the essays translates pretty safely to a 5? or is it borderline 4/5?
maxyboy — i wish i had seen that earlier :P</p>
<p>Do we need to know specific percentages, like the percentage of fish, the infrastructure of bolder city, size of redwoods, increase in extinction rates recently etc?</p>
<p>Cause i will fail if we need to memorize that useless propaganda.</p>
<p>does anyone know what the (rough) number of points total (or the mc/fr breakdown) to get a 5 is? for a 4?</p>
<p>How do you solve this problem?
After 200 million years, only 1/16 of the original amount of a radioactive waste will remain. The half-life of this radioactive waste is how many million years?
I know how to do the opposite, but not his.
5 steps to 5 never show how!</p>