Math Problem Statement

A frustum is formed by removing a small square-based pyramid from a similar, larger one. Work out the surface area of the frustum.

Solution

To calculate the surface area of the frustum, we need to address two components: the lateral (side) surface area and the areas of the top and bottom square faces.

1. Base Areas:

  • The bottom face of the frustum is a square with a side length of 48 mm, so its area is: Abottom=482=2304 mm2A_{\text{bottom}} = 48^2 = 2304 \text{ mm}^2

  • The top face is a square with a side length of 37 mm, so its area is: Atop=372=1369 mm2A_{\text{top}} = 37^2 = 1369 \text{ mm}^2

2. Lateral Surface Area (Trapezoidal Faces):

Each lateral face is a trapezium (trapezoid), and we will compute the area of one trapezoidal face and multiply by 4 (since there are four lateral faces).

For one trapezium, the parallel sides are the heights of the top and bottom squares:

  • Larger base: 4848 mm
  • Smaller base: 3737 mm
    The slant height of each trapezoid face is given as 37 mm.

The area of a trapezium is: Atrapezium=12×(b1+b2)×hA_{\text{trapezium}} = \frac{1}{2} \times (b_1 + b_2) \times h Where:

  • b1=48b_1 = 48 mm (larger base),
  • b2=37b_2 = 37 mm (smaller base),
  • h=37h = 37 mm (slant height).

Now, calculate the area: Atrapezium=12×(48+37)×37=12×85×37=1572.5 mm2A_{\text{trapezium}} = \frac{1}{2} \times (48 + 37) \times 37 = \frac{1}{2} \times 85 \times 37 = 1572.5 \text{ mm}^2

Since there are four trapezoidal faces, the total lateral surface area is: Alateral=4×1572.5=6290 mm2A_{\text{lateral}} = 4 \times 1572.5 = 6290 \text{ mm}^2

3. Total Surface Area:

The total surface area of the frustum is the sum of the top, bottom, and lateral surface areas: Atotal=Atop+Abottom+Alateral=1369+2304+6290=9963 mm2A_{\text{total}} = A_{\text{top}} + A_{\text{bottom}} + A_{\text{lateral}} = 1369 + 2304 + 6290 = 9963 \text{ mm}^2

Rounding to 1 decimal place, the surface area of the frustum is: Atotal9963.0 mm2A_{\text{total}} \approx 9963.0 \text{ mm}^2

Would you like more details or clarifications? Here are some additional questions for you:

  1. What is the formula for the volume of a frustum?
  2. How does the surface area of a frustum change if the slant height increases?
  3. Can we calculate the volume of this frustum with the given data?
  4. What is the relationship between a pyramid and its frustum?
  5. How would the surface area formula differ for a frustum of a cone?

Tip: Always check the unit consistency when working with area and volume problems.

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Math Problem Analysis

Mathematical Concepts

Geometry
Surface Area
Frustum

Formulas

Surface area of a square: A = side^2
Area of a trapezium: A = 0.5 * (b1 + b2) * height

Theorems

Pythagorean theorem (for slant height)

Suitable Grade Level

Grades 9-12