<p>I've done a couple math prep books that prepares you for the SAT, and they say that you have to know how to find prime factors, but i've done A LOT of practice tests and I have never come by these types of questions :( and insight?</p>
<p>Yes you do… to my understanding prime factoring means 45 = 3 * 3 * 5</p>
<p>In that case, collegeboard is very likely to ask something like “45 is equal to
a^2 * b”, what is the value of “ab”? (Interestingly, this is likely to be a medium or hard question, but once you learn how to do them, you can do them in like 10 seconds…)</p>
<p>The answer would be 15 of course.</p>
<p>^How would you solve that quickly? I can see how to solve that just plugging numbers in, but how can you solve it in under 10 seconds?</p>
<p>If you’ve seen this type of question enough times, you will realize right away how to do it. I do admit, 10 seconds is not enough time now that I think of it. 20-25 seconds on this type of question should be enough. Unless they ask you for a^3 * b^4 = 453 (where 453 is a large number that would take longer to factor, 453 is just an example). That would obviously take longer…</p>
<p>wow, that’s brilliant. I always just plug in numbers and guess.</p>
<p>BTW, on a ti-89:</p>
<p>factor(453) [enter]</p>
<p>3x151</p>
<p>factor (456) [enter]</p>
<p>2^3x3x19</p>
<p>…and yes, I know, you don’t need a calculator to get a 900 on this test…still a neat feature.</p>