# Finding the value of R/S

• Jul 27th 2011, 07:20 AM
IBstudent
Finding the value of R/S
Let A be the total area of 5 circles with radius R. And let B be the total area of 3 circles with radius R. If A=B. What is R/S ?

I know that A = 5(pie)*r^2 = 3(pie)*s^2 = B

So, how can I find the value of r and s?

• Jul 27th 2011, 07:26 AM
Prove It
Re: Finding the value of R/S
I don't know what you are using S to represent?
• Jul 27th 2011, 07:27 AM
Siron
Re: Finding the value of R/S
I guess s is the radius of the other 3 circles, try also not to use sometimes capital letters and sometimes small letters, that can be really confusing.
If you have:
$A=5\cdot \pi\cdot r^2$
$B=3\cdot \pi \cdot s^2$

If $A=B$ then indeed:
$5\cdot \pi \cdot r^2 = 3 \cdot \pi \cdot s^2$
$\Leftrightarrow \frac{r^2}{s^2}=\frac{3}{5}$

So ...
• Jul 27th 2011, 03:20 PM
mathjeet
Re: Finding the value of R/S
I think the radius of the second circle is S. if so you can solve for R/S as below;

A = 5. pi. R^2 and B = 3. pi. S^2

But A = B

Hence 5. pi. R^2 = 3. pi. S^2

R^2/S^2 = 3/5

or R/S = sqroot(3/5)