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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?

Learning
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E. sanders
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    What is the formula for the lateral area of a cone? – Bill O'Haran May 29 '18 at 14:43
  • What have you tried already? Hint: you'll probably need to rearrange the formula for lateral area, and replace the r in the formula by the value of radius you were given. You may also need Pythagoras. – bukwyrm May 29 '18 at 14:55

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$$LA(cone)=\pi r^2+\pi rl$$ 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.

Rhys Hughes
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