3-75 LA = SA=

Elementary Geometry For College Students, 7e
7th Edition
ISBN:9781337614085
Author:Alexander, Daniel C.; Koeberlein, Geralyn M.
Publisher:Alexander, Daniel C.; Koeberlein, Geralyn M.
ChapterP: Preliminary Concepts
SectionP.CT: Test
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Calculate LA and SA Left side: 19.5 in Middle: 247.75 in^2 Right: 12in
### Pentagonal Pyramid Surface Area Calculation

In this figure, we have a pentagonal pyramid with the following measurements:
- **Slant height**: 10.5 inches
- **Base area (B)**: 247.75 square inches
- **Base edge length**: 12 inches

We need to calculate the lateral area (LA) and surface area (SA) of the pyramid.

#### Lateral Area (LA) Calculation:

The lateral area of a pyramid can be calculated using the formula:
\[ LA = \frac{1}{2} \times P \times l \]
where:
- \( P \) is the perimeter of the base
- \( l \) is the slant height of the pyramid

#### Surface Area (SA) Calculation:

The surface area of a pyramid is given by:
\[ SA = LA + B \]
where:
- \( B \) is the area of the base

**Given Data:**
- Base edge length = 12 inches
- Number of base edges = 5 (since it's a pentagon)
- Slant height (\( l \)) = 10.5 inches
- Base area (\( B \)) = 247.75 square inches

**Step-by-step Calculation:**

1. **Calculate the perimeter \( P \) of the base:**
\[ P = 5 \times 12 = 60 \text{ inches} \]

2. **Calculate the lateral area \( LA \):**
\[ LA = \frac{1}{2} \times 60 \times 10.5 = 315 \text{ square inches} \]

3. **Calculate the surface area \( SA \):**
\[ SA = LA + B \]
\[ SA = 315 + 247.75 = 562.75 \text{ square inches} \]

Therefore:
\[ LA = 315 \text{ square inches} \]
\[ SA = 562.75 \text{ square inches} \]

This concludes our calculation for the lateral area and surface area of the given pentagonal pyramid.
Transcribed Image Text:### Pentagonal Pyramid Surface Area Calculation In this figure, we have a pentagonal pyramid with the following measurements: - **Slant height**: 10.5 inches - **Base area (B)**: 247.75 square inches - **Base edge length**: 12 inches We need to calculate the lateral area (LA) and surface area (SA) of the pyramid. #### Lateral Area (LA) Calculation: The lateral area of a pyramid can be calculated using the formula: \[ LA = \frac{1}{2} \times P \times l \] where: - \( P \) is the perimeter of the base - \( l \) is the slant height of the pyramid #### Surface Area (SA) Calculation: The surface area of a pyramid is given by: \[ SA = LA + B \] where: - \( B \) is the area of the base **Given Data:** - Base edge length = 12 inches - Number of base edges = 5 (since it's a pentagon) - Slant height (\( l \)) = 10.5 inches - Base area (\( B \)) = 247.75 square inches **Step-by-step Calculation:** 1. **Calculate the perimeter \( P \) of the base:** \[ P = 5 \times 12 = 60 \text{ inches} \] 2. **Calculate the lateral area \( LA \):** \[ LA = \frac{1}{2} \times 60 \times 10.5 = 315 \text{ square inches} \] 3. **Calculate the surface area \( SA \):** \[ SA = LA + B \] \[ SA = 315 + 247.75 = 562.75 \text{ square inches} \] Therefore: \[ LA = 315 \text{ square inches} \] \[ SA = 562.75 \text{ square inches} \] This concludes our calculation for the lateral area and surface area of the given pentagonal pyramid.
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