# Math Help - Circumference help needed...

1. ## Circumference help needed...

Hi there, I am not a math person at all and I need a math problem explained step by step in "dummy" terms to me so I can solve similar problems in the future!

Here is my sample problem:

C = πd (d = diameter)
A = πr² (the area of the circle is 9π)

What is the circumference of the circle?

Thanks!

2. Originally Posted by Southpaw22
Here is my sample problem:
C = πd (d = diameter)
A = πr² (the area of the circle is 9π)
What is the circumference of the circle?
The diameter is is twice the radius.
Area is $\pi r^2=9\pi$. Hint: $3^2=9$.

3. Thanks, but that didn't help me.

I need the solution explained step by step to me in "dummy" terms so that I can solve this type of problem in the future.

4. That isn't how it works here.

You know that $\pi\times r^2=\pi\times 9$

So $r^2=?$
So $r = ?$

Once you've found $r$,
The diameter is $2\times r$

Once you've found the diameter, the circumference is $\pi\times d$

5. Originally Posted by Southpaw22
I need the solution explained step by step to me in "dummy" terms so that I can solve this type of problem in the future.
That is not the way this forum works. SORRY
You should understand that this is not a homework service nor is it a tutorial service. Please either post some of your own work on these problems or explain what you do not understand about the question.

6. First of all, this isn't a homework question. I'm not in a math class, so I don't have any math homework. This problem is an example from the ACT practice booklet.

I'm taking the ACT test Saturday and I need to know how this type of problem is solved step by step so that I will know how to solve the ones on the ACT test.

What I don't understand is how the problem works or how it is solved, at all. I don't understand ANY of it.

What's the point of a math help forum if the helpers aren't truly willing to help in the way needed?

7. Originally Posted by Southpaw22
What's the point of a math help forum if the helpers aren't truly willing to help in the way needed?
The point is to make you sufficiently knowledgeable to solve this problem, and any future ones, for yourself. For us it's far easier to teach this once than it would be to answer each and every question. It's Math Help not Math Answers.

For the problem solve for r as has been done in post 2 and 4 and then find C.

8. Dear southpaw22,
Between now and Sat there is little you can do to improve your score.One important point - all these tests tend to confuse the taker. For example in this question you are given an equation for C in terms of diameter then give you an area in terms of r so you have to note this after you find r.Can you solve simple equations? And you know about pi ?

9. Originally Posted by Southpaw22
Hi there, I am not a math person at all and I need a math problem explained step by step in "dummy" terms to me so I can solve similar problems in the future!

Here is my sample problem:

C = πd (d = diameter)
A = πr² (the area of the circle is 9π)

What is the circumference of the circle?

Thanks!
Hi the circumference is the distance round the circle, so if you hold a glass in your hand and look at your hand and fingers rapping round it, the distance around it is the circumference, normally 360 degrees circle.

C = pie x distance = 3.142 x 960 = 3016.32

10. Originally Posted by David Green
C = pie x distance = 3.142 x 960 = 3016.32
Pie is an editable desert, (don't know about Shepard's).
And $\pi\ne 3.142$.

11. Originally Posted by Plato
Pie is an editable desert, (don't know about Shepard's).
And $\pi\ne 3.142$.
I prefer my pies to be edible but each to his own

$\pi \approx 3.142$ but I imagine the SAT will leave the answer in terms of pi (we don't do the SAT that American's do [although it does stand for Standardised Assessment Test(?) and nobody likes them, not even teachers])

12. That is spell check auto for you!