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Question
Consider the figure below.

(A triangular prism, or a pyramid with a triangular base, is shown. 

The triangular base has sides of 6 cm, 9 cm, and an unknown third side implied by the dashed lines, which creates a right angle. 

The sloping triangular face on top of the prism has a height of 8 cm. 

The sloping faces of the prism are colored peach/sand and the base is colored orange/burnt sienna. 

A dashed line, which suggests a height, extends from the apex of the triangular top face to the base of the prism. 

A label of 10 cm is on the right sloping face near its top edge. 

Labels show the dimensions of the base triangle: 6 cm, 9 cm, and another labeled side of 8 cm is visible.)

Determine the total surface area of the triangular prism. The formula chart is at the bottom of the page.

(5 points)
Area of ONE triangular face =
square centimeters

Area of the smallest rectangular face =
square centimeters

Area of the middle rectangular face =
square centimeters

Area of the largest rectangular face =
square centimeters

TOTAL Surface Area of the Triangular Prism =
square centimeters



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1 answer

To find the total surface area of the triangular prism, we need to calculate the areas of its components: the triangular bases and the rectangular faces.

Step 1: Area of the Triangular Face

The base of the triangular prism is a right triangle with the following sides: 6 cm, 8 cm, and 10 cm (since this forms a right triangle with the given sides).

To find the area of the triangular face, we can use the formula for the area of a triangle: \[ \text{Area} = \frac{1}{2} \times \text{base} \times \text{height} \] In our case, we can consider 6 cm as the base and 8 cm as the height, so: \[ \text{Area (Triangle)} = \frac{1}{2} \times 6 , \text{cm} \times 8 , \text{cm} = \frac{1}{2} \times 48 , \text{cm}^2 = 24 , \text{cm}^2 \]

Step 2: Area of the Rectangular Faces

The prism has three rectangular faces corresponding to the three sides of the triangular base.

  1. Smallest rectangular face (adjacent to the 6 cm base): \[ \text{Area} = \text{base} \times \text{height} = 6 , \text{cm} \times 10 , \text{cm} = 60 , \text{cm}^2 \]

  2. Middle rectangular face (adjacent to the 8 cm base): \[ \text{Area} = \text{base} \times \text{height} = 8 , \text{cm} \times 10 , \text{cm} = 80 , \text{cm}^2 \]

  3. Largest rectangular face (adjacent to the 9 cm base): \[ \text{Area} = \text{base} \times \text{height} = 9 , \text{cm} \times 10 , \text{cm} = 90 , \text{cm}^2 \]

Step 3: Calculate Total Surface Area

The total surface area of the prism can be calculated as follows: \[ \text{Total Surface Area} = 2 \times \text{Area of triangular face} + \text{Area of rectangular faces} \] \[ \text{Total Surface Area} = 2 \times 24 , \text{cm}^2 + 60 , \text{cm}^2 + 80 , \text{cm}^2 + 90 , \text{cm}^2 \] \[ = 48 , \text{cm}^2 + 60 , \text{cm}^2 + 80 , \text{cm}^2 + 90 , \text{cm}^2 \] \[ = 48 + 60 + 80 + 90 = 278 , \text{cm}^2 \]

Final Answers

  1. Area of ONE triangular face = 24 cm²
  2. Area of the smallest rectangular face = 60 cm²
  3. Area of the middle rectangular face = 80 cm²
  4. Area of the largest rectangular face = 90 cm²
  5. TOTAL Surface Area of the Triangular Prism = 278 cm²