# Thread: Geometry Problems

1. ## Geometry Problems

6. Circle A has a radius of 10 units and Circle B has a radius of 5 units. The center of Circle B is on the circumference of Circle A. What is the difference between the area which is within A but not B and the area which is within B but not A. Put your answer as a multiple of Pi.

30. Marna baked a batch of brownies in a 9x12 pan. She then decided to created a giant ice cream sandwich by cutting two congruent circular brownies out of the pan and placing a wedge of chocolate chip ice cream between them. What is the radius of the largest circular brownies she can cut? Express you answer as a common fraction in simplest radical form

2. ## Re: Geometry Problems

We can only help if you show your work, else we don't know where you're stuck.

3. ## Re: Geometry Problems

I don't know how to start. These questions are just to hard for me.

edit:
I just got (15√2 - 15 / 2) for #30. Can someone verify this for me?

4. ## Re: Geometry Problems

Originally Posted by MathStudent1999
I just got (15√2 - 15 / 2) for #30. Can someone verify this for me?
You're making me nervous! That comes out to ~3.1066 ; how did you get that?
By the way, your bracketing is not correct; should be: (15√2 - 15) / 2

I get (21 - SQRT(216) / 2 = ~3.1515 ; quite close to yours...

If we make the rectangle's sides a and b, then:
maximum radius of 2 inscribed circles = [a + b - SQRT(2ab)] / 2

5. ## Re: Geometry Problems

Originally Posted by Wilmer
You're making me nervous! That comes out to ~3.1066 ; how did you get that?
By the way, your bracketing is not correct; should be: (15√2 - 15) / 2

I get (21 - SQRT(216) / 2 = ~3.1515 ; quite close to yours...

If we make the rectangle's sides a and b, then:
maximum radius of 2 inscribed circles = [a + b - SQRT(2ab)] / 2
Is [a + b - SQRT(2ab)] / 2 a formula?

6. ## Re: Geometry Problems

Originally Posted by MathStudent1999
Is [a + b - SQRT(2ab)] / 2 a formula?
Call it whatever you want: it's the solution to your problem.
If it hasn't been used before (which I doubt), then I'm sure I'll get no Nobel prize!

Get some graph paper and try it using a 16 by 18 rectangle:
you'll get an exact 5 as radius of circles, which you'll be able
ti "fit in" perfectly; each circle is tangent to 2 sides,
plus the circles are tangent to each other...

7. ## Re: Geometry Problems

Okay but I probably got this wrong,I didn't look at the other answers or replies people gave because I want to figure this out too!!

Okay so, Circle A has a radius of 10 units and Circle B has a radius of 5 units. (That means A is bigger then B right?)

The center of Circle B is on the circumference of Circle A. What is the difference between the area which is within A but not B and the area which is within B but not A.
(That means it would be 5 units in difference)

Put your answer as a multiple of Pi. I don't know how to put it in pi! So can anyone tell me? I'm super stuck too.

Marna baked a batch of brownies in a 9x12 pan. She then decided to created a giant ice cream sandwich by cutting two congruent circular brownies out of the pan and placing a wedge of chocolate chip ice cream between them. What is the radius of the largest circular brownies she can cut? Express you answer as a common fraction in simplest radical form

I don't get how this is possible either cause there are two congruent circle shaped brownies but it never tells you the radius of those brownies! D:

8. ## Re: Geometry Problems

Alice, sorry, but you're making no sense...
the question is to calculate the radius; so radius sure won't be a given!

9. ## Re: Geometry Problems

Perhaps the intersecting area can be treated as an ellipse, then the minor axis is 5 units. Major axis ??