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A cylinder has a diameter of 32 feet and a height of 20 feet. a. Find the lateral area of the cylinder. b. Find the surface area of the cylinder.

Short Answer

Expert verified
a. 640Ï€ sq ft; b. 1152Ï€ sq ft

Step by step solution

01

Find the radius of the cylinder

The radius is half of the diameter. The diameter is given as 32 feet, so divide by 2 to get the radius:\[ \text{Radius} = \frac{32}{2} = 16 \text{ feet} \]
02

Calculate the lateral area of the cylinder

The lateral area of a cylinder is given by the formula \( 2 \pi r h \), where \( r \) is the radius and \( h \) is the height. Use \( r = 16 \) feet and \( h = 20 \) feet to substitute into the formula:\[ \text{Lateral Area} = 2 \pi (16)(20) = 640 \pi \text{ square feet} \]
03

Calculate the areas of the cylinder's top and bottom

Each end of the cylinder is a circle, and the area of a circle is \( \pi r^2 \). Calculate the area of one end using the radius from Step 1:\[ \text{Area of one end} = \pi (16)^2 = 256\pi \text{ square feet} \]Since there are two ends, multiply by 2:\[ \text{Total area of top and bottom} = 2 \times 256\pi = 512\pi \text{ square feet} \]
04

Calculate the total surface area of the cylinder

The total surface area of a cylinder is the sum of its lateral area and the areas of its two ends. Add the lateral area from Step 2 and the areas of the ends from Step 3:\[ \text{Surface Area} = 640\pi + 512\pi = 1152\pi \text{ square feet} \]

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Lateral Area
The lateral area of a cylinder is the surface area that wraps around the cylindrical shape, excluding the top and bottom ends. Imagine the label around a can. That's your lateral area! To find this, we use a simple formula:
  • Start with the formula: \( 2 \pi r h \) \( (r) \) is the radius, and \( (h) \) is the height of the cylinder.
  • Here, the symbol \( \pi \) represents the mathematical constant Pi (approximately 3.14159).
For our exercise, we calculated:
  • Radius \( (r) \) = 16 feet, Height \( (h) \) = 20 feet
  • Plug these values into the formula: \( 2 \pi (16)(20) \)
  • The lateral area results in \( 640\pi \) square feet.
This area is important if you're determining materials needed to wrap something around the cylinder.
Cylinder Height
The height of a cylinder is the distance between its two circular bases. Think of it as how tall the cylinder stands. It's a straightforward concept but crucial for calculating both the lateral and the total surface area of the cylinder.
  • In this problem, the height \((h)\) is given as 20 feet.
  • It's used in the calculation for the lateral area: \( 2 \pi r h \).
Remember:
  • The height doesn't affect the size of the top and bottom circles, but it greatly influences the lateral area.
  • A taller cylinder will have more surface to "wrap," increasing its lateral area.
Understanding height helps in various real-world scenarios, like optimizing storage space or designing labels.
Cylinder Radius
The radius of a cylinder is a key measurement, as it is half the diameter of the circular base. For our problem:
  • Given a diameter of 32 feet, the radius \((r)\) is half of this: \( \frac{32}{2} = 16 \) feet.
  • This radius is crucial for multiple calculations, like finding the lateral area and the areas of the top and bottom circles.
For calculation purposes:
  • The lateral area depends on the radius: \( 2 \pi r h \)
  • The area of each circle at the ends (top and bottom) is \( \pi r^2 \)
In our example, the radius was used to calculate:
  • Lateral Area: \( 2 \pi (16)(20) = 640\pi \)
  • Area of each circle: \( \pi (16)^2 = 256\pi \)
Understanding the radius is essential when dealing with any sort of round objects or shapes.

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