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# Cylinders

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The height of a right cylinder is 2.5 times its radius. If the surface area of the cylinder is $$448 \pi$$, what is the radius of the cylinder in centimeters?

Apr 13, 2022

#1
+579
+3

Area of cylinder: $$2\pi r^2+2\pi rh$$

$$2\pi \:\:r^2+2\pi \:\:r\left(2.5r\right)$$

$$7\pi \:r^2=448\pi$$

$$r=-8,\:r=8$$

But a radius can't be negative so our radius is $$8$$!!!

Apr 13, 2022

#1
+579
+3

Area of cylinder: $$2\pi r^2+2\pi rh$$

$$2\pi \:\:r^2+2\pi \:\:r\left(2.5r\right)$$

$$7\pi \:r^2=448\pi$$

$$r=-8,\:r=8$$

But a radius can't be negative so our radius is $$8$$!!!

Vinculum Apr 13, 2022