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What is a rectangular prism?

A rectangular prism, also known as a cuboid, is a three-dimensional solid that has six faces, all of which are rectangles. Rectangular prisms are one of the most fundamental shapes in mathematics and science, playing a key role in calculations across various fields, such as physics, engineering, and architecture.

A rectangular prism can be defined by three dimensions: length (l), width (w), and height (h). These dimensions run perpendicular to each other, forming a right angle where their faces meet. Each face of the rectangular prism is a rectangle, and opposite faces are identical rectangles.

Formulae for calculations

Using the dimensions of a rectangular prism, you can calculate various properties of the shape. Below are the formulae used for these calculations.

Volume of a rectangular prism

The volume (V) of a rectangular prism is the product of its length, width, and height:

V=l×w×hV = l \times w \times h

Where:

  • ll is the length,
  • ww is the width,
  • hh is the height.

Surface area of a rectangular prism

The surface area (SA) of a rectangular prism is calculated by summing the areas of all six rectangular faces:

SA=2(lw+lh+wh)SA = 2(lw + lh + wh)

This formula accounts for the fact that each of the three unique pairs of opposite rectangular faces consists of two rectangles of equal area.

Diagonal of a rectangular prism

The diagonal (d) is the main diagonal that runs from one vertex of the prism to another vertex, passing through the interior of the prism:

d=l2+w2+h2d = \sqrt{l^2 + w^2 + h^2}

This uses the Pythagorean theorem in three dimensions.

Practical examples

Example 1: Calculating the volume

Consider a rectangular prism with a length of 5 meters, a width of 3 meters, and a height of 2 meters. Plug these values into the formula for volume:

V=5×3×2=30cubic metersV = 5 \times 3 \times 2 = 30 \, \text{cubic meters}

Example 2: Calculating the surface area

For the same rectangular prism:

SA=2(5×3+5×2+3×2)=2(15+10+6)=2×31=62square metersSA = 2(5 \times 3 + 5 \times 2 + 3 \times 2) = 2(15 + 10 + 6) = 2 \times 31 = 62 \, \text{square meters}

Example 3: Calculating the diagonal

Using the given values for length, width, and height:

d=52+32+22=25+9+4=386.16metersd = \sqrt{5^2 + 3^2 + 2^2} = \sqrt{25 + 9 + 4} = \sqrt{38} \approx 6.16 \, \text{meters}

Historical context

The concept of a prism can be traced back to ancient Greece, where it played a significant role in Euclidean geometry. These geometric principles laid the groundwork for more complex mathematical and physical models. Even in ancient times, structures resembling modern prisms were built, demonstrating an early understanding of this three-dimensional form.

Notes on usage

  • Ensure that all dimensions are in the same unit when calculating volume, surface area, or diagonal.
  • Rectangular prisms are prevalent in daily life, seen in objects like bricks, boxes, and buildings, making these calculations relevant in various everyday applications.
  • Altering any dimension while keeping others constant will proportionally affect the resulting volume, surface area, and diagonal measurement.
  • Rectangular prism is the same as cuboid or parallelepiped.

Frequently asked questions

How do you find the volume of a rectangular prism with side lengths 8 cm, 6 cm, and 10 cm?

You calculate the volume by multiplying all the side lengths:

V=8×6×10=480cubic centimetersV = 8 \times 6 \times 10 = 480 \, \text{cubic centimeters}

What is the surface area of a cuboid with dimensions 7 m, 4 m, and 3 m?

The surface area is calculated as follows:

SA=2(7×4+7×3+4×3)=2(28+21+12)=2×61=122square metersSA = 2(7 \times 4 + 7 \times 3 + 4 \times 3) = 2(28 + 21 + 12) = 2 \times 61 = 122 \, \text{square meters}

How many diagonals does a rectangular prism have?

A rectangular prism has four space diagonals which pass through the interior connecting opposite vertices, and twelve face diagonals.

Why is it important to calculate the diagonal of a rectangular prism?

Calculating the diagonal is important for determining the distance through the interior, which is crucial in packing, transportation optimization, and when determining material requirements in construction.