<p>Does anyone remember the exact question with the circles inside of each other and you had to determine the area of the shaded region?</p>
<p>Would anyone mind drawing it up on paint and including the question and an explanation (explanation and question can be posted here). </p>
<p>This is the only question I do not know the answer to and any help would be appreciated.</p>
<p>Thanks,
JR</p>
<p>Well, there was 4 circles. They had diameters of 3,4,5,6,</p>
<p>The question looked for the area of the the 3rd circle minus the area of the second. So,
pi(r1)^2 - pi(r2)^2
r1 = 5/2
r2 = 4/2 = 2</p>
<p>So, (25/4)pi - 4 pi = (9/4) pi.</p>
<p>Hope that helps.</p>
<p>can someone PLEASE draw it up on paint and put it on tinypic or something??</p>
<p>Pretty sure, but of course there is a chance for error. But that answer is a large consensus on the discussion thread.</p>
<p>it's 9∏/4 definitely.</p>
<p>can i still get a 800 if i got this one wrong and nothing else?</p>
<p>Depends on the curve, I guess.</p>
<p>likely? or unlikely? i am REALLY needing an 800 on math to make up for my 600s on the other sections!</p>
<p>its definately that answer that was posted previously.</p>
<p>It's definitely 9pi/4.</p>
<p>You still want that diagram?</p>
<p>Anyway, here it is: <a href="http://dl.getdropbox.com/u/2619/Circles.png%5B/url%5D">http://dl.getdropbox.com/u/2619/Circles.png</a></p>
<p>AB=BC=CD=1 and D is the center of the largest circle.</p>
<p>ok so what am i missing????</p>
<p>i still don't get it.</p>
<p>AB=BC=CD=1.. meaning the radius of the largest circle is 3.....
meaning the area is 9pi... w hat am i donig wrong?</p>
<p>Okay, look. If AB+BC+CD=3, and AD is the radius of the largest circle, then DE is also 3, right? (It's also the radius).</p>
<p>So the [diameter] of the second largest circle is 3+1+1=5, and it's radius is 2.5 or 5/2.</p>
<p>The diameter of the second smallest circle is 3+1=4, and it's radius is two.</p>
<p>Area of Second Largest - Area of Second Smallest = [(5/2)^2]∏ - [2^2]∏</p>
<p>And that works out to be 9∏/4.</p>
<p>DAMNIT! i used the largest circle! ***!</p>
<p>5/2 = 2.5
2.5^2 = 6.25 and then times pi.</p>
<p>4/2 = 2
2^2=4 and then times pi.</p>
<p>6.25pi - 4pi = 2.25pi or 9pi/4</p>
<p>To find the shaded area, you need to do: area of Circle B - area of Circle C.</p>
<p>We know that AD = DE because D is the midpoint of the circle. AD is 3, therefore, DE is 3.</p>
<p>To find the area of circle B, you need to find the radius. The diameter is: DE (3) + BC(1) + CD(1).
Therefore, the radius is half of this, which is 5/2. </p>
<p>To find the area of circle C, you need to find the radius. The diameter is: DE (3) + CD(1).
Therefore, the radius is half of this, which is 2. </p>
<p>Next, do as was stated earlier: area of Circle B - area of Circle C.</p>
<p>2.5^2 PI - 2^2 PI = 9/4 PI</p>
<p>Hey I just wrote this into the wrong topic :(</p>
<p>Hey guys,</p>
<p>last night, people werent sure whether 9/4 Pi or 5 Pi was the right answer for the circle question.
So I couldnt sleep (lol) and had this stupid explanation for 9/4 Pi in my head:
All we know is the relative distance between the circles and the big circle and the middle point of the big circle.
The circle middlepoints are all the same horizontally, but have been moved vertically. So we know that the shaded circle has a distance of 1 to the big circle. We want to make his middlepoint the same as the middlepoint of the big circle, so we move him up by 0.5. The shaded circle now has a distance of 2.5 to the middlepoint of the big circle, as he has got the same middlepoint, his radius is 2.5
The distance between the smaller circle and the big circle is 2, we therefore move him up by 1. He now has a radius of 2.
2.5=5/2
A1 = Pi 25/4
A2 = Pi 4 = Pi 16/4
A1-A2 = Pi 9/4</p>
<p>Is this right?
Pleaaaaaaaaaaaase</p>
<p>@Rangzen -> I really don't understand what you mean, but 9∏/4 is correct. Did you see the way I did it? (Posts #13 and #15)</p>
<p>9pi/4 </p>
<p>:)</p>
