Math Problem Statement

In the figure, the volume of the prism is 480 cm³. (a) Find the value of h. (b) Find the total surface area of the prism.

Solution

Let's solve this problem step-by-step.

Problem Analysis

We are given:

  1. The volume of the prism is 480cm3480 \, \text{cm}^3.
  2. The prism has a triangular cross-section with dimensions:
    • Base of the triangle: 13cm13 \, \text{cm}
    • Height of the triangle: hcmh \, \text{cm} (which we need to find)
    • Length of the prism: 24cm24 \, \text{cm}
    • Width of the prism (the perpendicular side): 8cm8 \, \text{cm}

The task is to:

  1. Find the value of hh (the height of the triangle).
  2. Find the total surface area of the prism.

Solution

(a) Finding the value of hh

The volume of a prism with a triangular cross-section is given by: Volume=Area of cross-section×Length\text{Volume} = \text{Area of cross-section} \times \text{Length}

The area of the triangular cross-section is: Area of triangle=12×Base×Height=12×13×h\text{Area of triangle} = \frac{1}{2} \times \text{Base} \times \text{Height} = \frac{1}{2} \times 13 \times h

So, the volume of the prism can be written as: 480=(12×13×h)×24480 = \left( \frac{1}{2} \times 13 \times h \right) \times 24

Solving for hh:

  1. Simplify the equation: 480=13×h×242480 = \frac{13 \times h \times 24}{2} 480=13×h×12480 = 13 \times h \times 12
  2. Divide both sides by 13×1213 \times 12: h=48013×12=480156h = \frac{480}{13 \times 12} = \frac{480}{156}
  3. Calculate hh: h=3.08cm (approximately)h = 3.08 \, \text{cm (approximately)}

(b) Finding the total surface area of the prism

The surface area of the prism includes:

  1. Two triangular faces.
  2. Three rectangular faces (one for each side of the triangle).
1. Area of the triangular faces

The area of each triangular face is: Area of triangle=12×13×3.08=20.02cm2\text{Area of triangle} = \frac{1}{2} \times 13 \times 3.08 = 20.02 \, \text{cm}^2

Since there are two triangular faces: Total area of triangles=2×20.02=40.04cm2\text{Total area of triangles} = 2 \times 20.02 = 40.04 \, \text{cm}^2

2. Area of the rectangular faces
  • Face 1 (base 13cm13 \, \text{cm} by length 24cm24 \, \text{cm}): 13×24=312cm213 \times 24 = 312 \, \text{cm}^2
  • Face 2 (height 3.08cm3.08 \, \text{cm} by length 24cm24 \, \text{cm}): 3.08×24=73.92cm23.08 \times 24 = 73.92 \, \text{cm}^2
  • Face 3 (width 8cm8 \, \text{cm} by length 24cm24 \, \text{cm}): 8×24=192cm28 \times 24 = 192 \, \text{cm}^2

Adding the areas of the three rectangular faces: 312+73.92+192=577.92cm2312 + 73.92 + 192 = 577.92 \, \text{cm}^2

Total Surface Area

Combining the areas of the triangular and rectangular faces: Total Surface Area=40.04+577.92=617.96cm2\text{Total Surface Area} = 40.04 + 577.92 = 617.96 \, \text{cm}^2

Final Answers

  1. h=3.08cmh = 3.08 \, \text{cm}
  2. Total surface area of the prism = 617.96cm2617.96 \, \text{cm}^2

Would you like a detailed explanation of any part of the solution, or have additional questions? Here are some related questions to expand understanding:

  1. What would change in the calculations if the length of the prism increased?
  2. How does the surface area formula differ for prisms with different cross-sectional shapes?
  3. How would the volume change if the height hh was doubled?
  4. What other geometric formulas could help solve similar volume problems?
  5. How would you find the surface area if the triangular cross-section was an equilateral triangle?

Tip: Always confirm all given dimensions and units in geometry problems before starting the calculations to avoid mistakes.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Volume of Prisms
Surface Area of Prisms
Geometry

Formulas

Volume of a prism = Area of cross-section × Length
Area of a triangle = (1/2) × Base × Height
Surface Area of prism = 2 × Area of triangular face + Sum of areas of rectangular faces

Theorems

Volume and Surface Area of Prisms

Suitable Grade Level

Grade 9