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Test Preparation
1

<p>In a given geometric sequence gn, g4 = 5 and g6 = 11.25. What is g14 + g17?</p>

<p>(A) 8/27<br>
(B) 4/9<br>
(C) 2/3<br>
(D) 8/9<br>
(E) 9/8</p>

2

<p>what test is it for??? IIIC??? (i know theres no such thing; it signifies the difficulty level)</p>

3

<p>Math iic. From sparknotes.</p>

4

<p>you sure its a geometric sequence? cuz something just doesnt seem right about those answers.</p>

5

<p>Unless I'm missing something, there's a serious mistake in the problem. Geometric sequences simply involve multiplying each term by a constant (I'll call it x) to get the next term. If g4 = 5, then g5 = 5x and g6 = 5x^2. So 5x^2 = 11.25, which makes x = 1.5. If you decide to muscle through it instead of figuring out the formula for geometric sequences, just keep multiplying terms by 1.5 to get the next term. The numbers can't be as small as the answer choices. I think Sparknotes made a bad Q.</p>

6

<p>You have misread the question or sparknotes has a mistake (unsurprisingly). </p>

<p>It asks to find g14 / g17. (that is the ratio between the members)
From the formulas for geometric sequence we have gN=g1*q^(N-1) , where gN is the N-th member, g1 is the first member, q is the quotient.</p>

<p>g4=5 => g1<em>q^3=5 (1)
g6=11.25 => g1</em>q^5=11.25 (2)</p>

<p>dividing the equations, we get q^2=2.25, that is q=1.5=3/2 this is the quotient</p>

<p>g17=g1<em>q^16
g14=g1</em>q^13</p>

<p>dividing both equations</p>

<p>g14/g17=1/q^3, but we now know that q=3/2. so:</p>

<p>g14/g17=1/[(3/2)^3]=1/(27/8)=8/27.</p>

<p>so (A) is the correct answer.</p>

7

<p>"divided by" makes a lot more sense! :) Good spot Victor.</p>

8

<p>Nope, it said to add. Way to go Sparknotes!!!!! No wonder I couldn't get it!!!!!!!!!!!!!!!! That's one more question I would've gotten right! YEAH (Not that it really matter, I got an 800; sorry if that was egotistical)</p>

9

<p>dick. i spent 5 minutes working on that.</p>

10

<p>...
i have the sparknotes book and it says divide, not add</p>

11

<p>Go online to practice test 1 and it clearly says to add...</p>

12

<p>where can you find the sparknotes math IIC section online?</p>

13

<p>sparknotes.com Go to the sat II section.</p>