Surface Area of Rectangular Prism: Express in Terms of a, b, and c

Question

Express the surface area of the rectangular prism below in terms of a, b, and c.

cccaaabbb

Video Solution

Solution Steps

00:00 Express the surface area of the box
00:03 We'll use the formula for calculating rectangle area (side times side)
00:11 Let's calculate the area of each face
00:34 Since the box has 6 faces (2 of each type)
00:39 To calculate the surface area, we'll multiply each area by 2 and sum
00:53 And this is the solution to the question

Step-by-Step Solution

The problem requires us to find the surface area of a rectangular prism in terms of aa, bb, and cc. To find this, we use the standard formula for the surface area of a cuboid.

The surface area of a cuboid is given by:

S=2(ab+bc+ca) S = 2(ab + bc + ca)

Explanation of the formula:

  • Each face of the cuboid is a rectangle. There are three unique rectangles in a cuboid:
  • Two faces with dimensions a×ba \times b,
  • Two faces with dimensions b×cb \times c,
  • Two faces with dimensions c×ac \times a.

These three pairs of faces contribute to the total surface area as follows:

  • Area of the two a×ba \times b faces: 2×(ab)2 \times (ab)
  • Area of the two b×cb \times c faces: 2×(bc)2 \times (bc)
  • Area of the two c×ac \times a faces: 2×(ca)2 \times (ca)

Adding these areas together gives us the total surface area:

S=2ab+2bc+2ca S = 2ab + 2bc + 2ca

This simplifies to 2(ab+bc+ca)2(ab + bc + ca).

Given the choices, the correct expression for the surface area is 2ac+2ab+2bc2ac + 2ab + 2bc.

Answer

2ac+2ab+2bc