Chapter 9: Problem 3
For the right circular cylinder, suppose that \(r=5\) in and \(h=6\) in. Find the exact and approximate a. lateral area. b. total area. c. volume. (figure cannot copy)
Short Answer
Expert verified
a. Exact lateral area: \( 60\pi \), Approximate lateral area: 188.496 in². b. Exact total area: \( 110\pi \), Approximate total area: 345.576 in². c. Exact volume: \( 150\pi \), Approximate volume: 471.24 in³.
Step by step solution
01
Understanding the Formula for Lateral Area
The lateral area of a right circular cylinder can be found using the formula \( A_l = 2\pi rh \), where \( r \) is the radius and \( h \) is the height of the cylinder. Given \( r = 5 \) inches and \( h = 6 \) inches, we substitute these values into the formula.
02
Calculating the Exact Lateral Area
Substituting the given values into the formula gives us: \( A_l = 2\pi (5)(6) = 60\pi \) square inches. This is the exact lateral area.
03
Approximating the Lateral Area
To find the approximate lateral area, substitute \( \pi \approx 3.1416 \) into the formula: \( A_l \approx 60 \times 3.1416 = 188.496 \) square inches.
04
Understanding the Formula for Total Area
The total area of a cylinder is given by the formula \( A_t = 2\pi r(h+r) \). This accounts for both the lateral surface area and the area of the circular bases. Substituting our known values: \( r = 5 \), \( h = 6 \).
05
Calculating the Exact Total Area
Substitute the values into the formula: \( A_t = 2\pi (5)(6+5) = 2\pi (5)(11) = 110\pi \) square inches. This is the exact total area.
06
Approximating the Total Area
Substitute \( \pi \approx 3.1416 \) to approximate the total area: \( A_t \approx 110 \times 3.1416 = 345.576 \) square inches.
07
Understanding the Formula for Volume
The volume of a right circular cylinder is given by \( V = \pi r^2 h \). We will use this formula with \( r = 5 \) and \( h = 6 \).
08
Calculating the Exact Volume
Substituting the values, we obtain: \( V = \pi (5)^2(6) = 150\pi \) cubic inches. This is the exact volume.
09
Approximating the Volume
To find the approximate volume, we substitute \( \pi \approx 3.1416 \) into our formula: \( V \approx 150 \times 3.1416 = 471.24 \) cubic inches.
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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 refers to the surface area of the cylinder excluding the circular bases. Think of it as the label on a can, which rolls around the side of the cylinder. This area is calculated with the formula \( A_l = 2\pi rh \), where \( r \) denotes the radius and \( h \) the height of the cylinder.
To break it down easily:
This concept becomes handy in real-life situations, such as determining how much material is needed to cover the surface of cylindrical containers.
To break it down easily:
- "2\pi r" represents the circumference of the circular base. It's like wrapping a string around the base.
- "h" represents the height, showing how tall the side extends upward.
This concept becomes handy in real-life situations, such as determining how much material is needed to cover the surface of cylindrical containers.
Total Area
When thinking about the total area of a cylinder, consider the entire exterior surface, which includes both the lateral area and the area of the two circular ends or bases. The formula to compute this is \( A_t = 2\pi r(h + r) \). Let's dive into the components:
Total surface area is crucial when you need to evaluate how much paint is required to cover a cylindrical surface entirely, for instance.
- "2\pi r" again signifies the circumference of the circular base.
- "h + r" combines the cylinder’s height with its radius.
- This overall formula bundles the inner and outer circumferences and heights.
Total surface area is crucial when you need to evaluate how much paint is required to cover a cylindrical surface entirely, for instance.
Volume
The volume of a cylinder quantifies how much space it occupies, essentially answering the question of how much liquid, grain, or any other material it can hold. For a right circular cylinder, this is calculated through \( V = \pi r^2 h \). Breaking it down, we have:
Understanding volume helps in practical applications like finding out the exact quantity of liquid a tank can hold, proving beneficial for manufacturers and engineers alike.
- "\( \pi r^2 \)" calculates the area of one base, representing a filled circle.
- Multiplying by the height "h" extends this circular base through the height, forming the 3D space.
Understanding volume helps in practical applications like finding out the exact quantity of liquid a tank can hold, proving beneficial for manufacturers and engineers alike.