Homework Help: Calculus - Algebra question

1. Feb 25, 2005

lektor

The Numerical Values of the circumference and area of a circle add up to 16.
Determine the radius to 4 sf.

Well so far me and my friend have been working on this and all of our results have been different to the final question, :<

We first tried to manipulate with the formula pi x r^2 = a without any success, it would be appreciated if someone could clarify this question.

Yes, maybe not a very hard question but it has confused us.

Last edited: Feb 25, 2005
2. Feb 25, 2005

Integral

Staff Emeritus
You know that the:

Area + Circumferance = 16

Area = $\pi r^2$
Circuference = $\pi r$

all you need do is solve the above relationship for r.

3. Feb 25, 2005

danne89

Denote the area as x and the circumference as y
x + y = 16
x=Pi(y/2)^2

Then substitute y in terms of x in the second equation and solve it.

4. Feb 25, 2005

scholar

Probably a typo, but I'm fairly sure that Circuference = $2\pi r$

5. Feb 25, 2005

lektor

hah

we had actually already got it, but we messed up the quadractic formula calculation.

Btw for thoose who are wondering the answer was 1.4683

6. Feb 25, 2005

WORLD-HEN

why is this a "calculus-algebra" question?

7. Feb 25, 2005

lektor

In the New Zealand Curriculum.

Caculus is comprised of

Complex numbers/algebra
Differentiation
Intergration
Conics

So by New Zealand standards this is an Calculus - Algebra question

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook