<p>13.</p>
<p>If the first two terms of a geometric sequence are 5 and 10 what is the 4th term of the sequence?</p>
<p>Dude, that's frickin' impossible. Don't even bother.</p>
<p>I think it's 40.</p>
<p>Geometric</a> Sequences by MATHguide</p>
<p>r = 10/5
r = 2</p>
<p>a(4) = a(1) r^n-1
a(4) = 5 r^(4-1)
a(4) = 5 r^3
a(4) = 5 x 8</p>
<p>a(4) = 40</p>
<p>(I never actually learned this in school I just remember seeing this in a PSAT prep book and googled it for a refresher, might be wrong).</p>
<p>yup its obvious.
There's a formula for it i forgot ... but b/c it says geometric u know that 10/5 = 2
So 10 x 2 = 20
20 x 2 = 40</p>
<p>I believe the two above got it. A number called the ratio defines the next term in a geometric sequence. Term 1 x ratio = Term 2 and so on. So what times 5 = 10? It's 2. So the terms are
5, 10, 10x2, 10x2x2 or
5, 10, 20, 40</p>
<p>Yep, I read the first sentence of the link skatj gave and thought of 40. Now I've learned something, too!</p>
<p>The question is quite easy. The answer is 40.
Using the formula; ar^(n-1), where a= first term
r= common ratio
Here, a=5, r=2 and n-which is the term we are looking for-equals 4. When you substitute the above values in the eqn, you 'll get 40. I hope you understand 'cos I find it hard to explain Math this way.</p>
<p>40 is confirmed.</p>
<p>I'm pretty sure this was actually a joke. Hence the "super uber hard" label on a really easy problem and the wink after the thread.</p>
<p>Yeah, you CC guys really have no sense of humor, do you?</p>
<p>^we have a sense of humor (or at least i do), but it seemed as though the guy actually wanted help. whatever.</p>