Question

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An illustration shows a three dimensional composite figure formed by a smaller rectangular prism connected to a larger rectangular prism. The top, right, and front faces are visible. The faces and edges that are not visible are indicated by dashed lines. The rectangular prism on the left has a length of 10 millimeters a height of 8 millimeters. The width of the rectangular prism is not shown, but it aligns perfectly with the width of the rectangular prism on the right. The rectangular prism on the right has a length of 6 millimeters, a width of 6 millimeters, and a height 6 of millimeters. The combined length of the two rectangular prisms measures 16 millimeters.



What is the total surface area of the figure?

(1 point)
mm2
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1 answer

To find the total surface area of the composite figure made up of the two rectangular prisms, we will calculate the surface area of each prism separately and then account for the areas that are not exposed.

  1. Rectangular Prism on the Left:

    • Length (L) = 10 mm
    • Height (H) = 8 mm
    • Width (W): We can find W since the total length (L1 + L2) = 16 mm and the length of the right prism (L2) is 6 mm, thus: \( W = 16 mm - 10 mm = 6 mm \).
    • The dimensions of the left prism are therefore: \( L = 10 \) mm, \( W = 6 \) mm, \( H = 8 \) mm.

    The surface area \( A \) of a rectangular prism is calculated by the formula: \[ A = 2(LW + LH + WH) \] Plugging in the values: \[ A_{left} = 2(10 \times 6 + 10 \times 8 + 6 \times 8) \] \[ = 2(60 + 80 + 48) = 2(188) = 376 \text{ mm}^2 \]

  2. Rectangular Prism on the Right:

    • Length (L) = 6 mm
    • Width (W) = 6 mm
    • Height (H) = 6 mm

    Using the surface area formula again: \[ A_{right} = 2(6 \times 6 + 6 \times 6 + 6 \times 6) \] \[ = 2(36 + 36 + 36) = 2(108) = 216 \text{ mm}^2 \]

  3. Subtracting the Overlap: Since the two prisms are combined, the area of the face where they join (the front face of the left prism that overlaps with the right prism) is counted twice. This face has dimensions:

    • Height = 6 mm (matching the right prism)
    • Width = 6 mm

    The area of this face is: \[ A_{overlap} = H \times W = 6 \times 6 = 36 \text{ mm}^2 \]

  4. Total Surface Area Calculation: Combine the surface areas of both prisms and subtract the overlapping area: \[ A_{total} = A_{left} + A_{right} - A_{overlap} \] \[ = 376 + 216 - 36 = 556 \text{ mm}^2 \]

Therefore, the total surface area of the figure is \( \boxed{556} \) mm\(^2\).