# Question: Intersecting Circles

## Comment on Intersecting Circles

### Thanks you so mush for the

Thanks you so much for the videos. I just completed watching all videos of geometry. This is a great help for me. I have learned a lot. Hope this will help me for my gmat preparation.

### This is blowing my mind

This is blowing my mind

### alternatively to the formula:

alternatively to the formula: drop an altitude, which results in two 90:60:30 triangles. From there base will be half the hypotenuse = 6/2=3 and therefore hight will be 3*root3

then are as usual: (b*h)/2 --> (6*3*root3)/2

That works too!

### if you start of with this can

if you start of with this can you solve the problem by eliminating all solutions that don't include -18root3? or would it be a wild guess?
?

### Great idea!

Great idea!

We know that the area of ONE equilateral triangle is 9√3
So, once you're certain how many equilateral triangle areas you need to subtract (in this case, we must subtract 2 of those areas), then you can start eliminating.

Cheers,
Brent

### Does this qs also deserve a

Does this qs also deserve a 700-800 category listing? Mind blowing...

### Yes, this is definitely a 700

Yes, this is definitely a 700+ level question. VERY tricky!

Aside: if you hover your cursor over each colored square next to the PLAY button, you'll see the difficulty level of each question.

Green: 350 - 500
Yellow: 510 - 650
Red: 660 - 800

Cheers,
Brent

### If you go here (https://www

If you go here (https://www.gmatprepnow.com/content/free-content), you'll find a downloadable pdf of all GMAT math flashcards. They contain more than just Geometry, but I think they're useful.

### man!! i am in love with your

man!! i am in love with your videos

Thanks for that!

### Hi Brent, I solved this

Hi Brent, I solved this question with the following approach:

Let the two intersecting points be AB. Draw AB and OP. Let them intersect at X. Area of sector OAB is 12pi. Area of triangle OAB is 9*root(3)

Since the area that we have to find is twice of 12pi - 9*root(3), answer is 24pi - 18root(3)

Nice work!!

### Question: DO we have to

Question: DO we have to remember the formula of a sphere's volume

### No, you don't need to

No, you don't need to memorize the formula for the volume of a sphere.
If the GMAT were to create a question involving a sphere's volume, they will undoubtedly provide the necessary formula.
Here's an example of such a question: https://gmatclub.com/forum/the-volume-of-a-sphere-with-radius-r-is-4-3-p...

### Another great video Brent and

Another great video Brent and mind blowing. To clarify, when we calculate a+b area, is this belong to circle C or P or both? Same with rest b+c areas...etc. Thanks Brent

### All parts inside the blue

All parts inside the blue (and the later yellow) area belong to BOTH circles .

### Thanks Brent for confirmation

Thanks Brent for confirmation. Now I'm clear that for common area calculation of both circle is same as circumference area calculation except to deduct the duplicate b,d part.