To find r, you can multiply both sides by πr²
[tex]513\times \pi r^2 = \frac{79000}{\pi r^2} \times \pi r^2\\\\ 513\pi r^2 = 79000[/tex]
You would then get:
513πr² = 79,000
Then to isolate r, you can divide 513π on both sides.
(513πr²)/(513π) = 79,000/(513π)
r² = 79,000/(513π)
To finally get r, you can take the square root of both sides.
[tex]\sqrt{r^2} = \sqrt{\frac{79000}{513 \pi}}\\\\r = \sqrt{\frac{79000}{513 \pi}} \approx \boxed{7.001} [/tex]
