Math Problem Statement

What is the surface area of the pyramid with a square base if e = m = 5 inches?

(A) 5 + 5√3 in2

(B) 5 + 25√3 in2

(C) 25 + 25√3 in2

(D) 125 + 25√3 in2

(E) 125√3 in2

Solution

To find the surface area of a pyramid with a square base, we need to calculate both the area of the base and the area of the triangular faces.

The surface area AA of the pyramid is given by:

A=Abase+Alateral facesA = A_{\text{base}} + A_{\text{lateral faces}}

Step 1: Area of the base

The base is a square, and the side length of the square is m=5m = 5 inches. The area of the square base is:

Abase=m2=52=25in2A_{\text{base}} = m^2 = 5^2 = 25 \, \text{in}^2

Step 2: Area of the lateral faces

The lateral faces of the pyramid are triangles. Each triangle has a base equal to m=5m = 5 inches, and the slant height of each triangle is denoted by e=5e = 5 inches.

The area of one triangular face is:

Atriangle=12×base×slant height=12×5×5=12.5in2A_{\text{triangle}} = \frac{1}{2} \times \text{base} \times \text{slant height} = \frac{1}{2} \times 5 \times 5 = 12.5 \, \text{in}^2

There are four triangular faces, so the total area of the lateral faces is:

Alateral faces=4×12.5=50in2A_{\text{lateral faces}} = 4 \times 12.5 = 50 \, \text{in}^2

Step 3: Total surface area

Now, we can find the total surface area by adding the area of the base and the lateral faces:

A=Abase+Alateral faces=25+50=75in2A = A_{\text{base}} + A_{\text{lateral faces}} = 25 + 50 = 75 \, \text{in}^2

Thus, the total surface area of the pyramid is 75 in², but none of the options match exactly. Let's check the information in the problem, where the slant height e=5e = 5 is used.

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Math Problem Analysis

Mathematical Concepts

Geometry
Surface Area
Pyramids

Formulas

Surface area of pyramid = Area of base + Area of lateral faces
Area of square base = m^2
Area of one triangular face = 1/2 * base * slant height
Total lateral area = 4 * Area of one triangular face

Theorems

Surface area of a pyramid
Area of a square
Area of a triangle

Suitable Grade Level

Grades 7-9