Lateral Area of a cone

Question

The lateral area of a cone is $574 \pi$ $cm^2$. The radius is $19.6$ cm. What is the slant height to the nearest tenth of a centimeter?

Answer 1

$$LA(cone)=\pi r^2+\pi rl$$ where $l$ is the slant height and $r$ the radius. Rearrange for: $$l=\frac{LA-\pi r^2}{\pi r}=\frac{LA}{\pi r}-r=\frac{574\pi}{19.6\pi}-19.6$$ and go from there.