A 3-dimensional object has height, width, and depth (thickness), like any object in the real world. A **polyhedron** is a 3-dimensional figure that has polygons as **faces**. A **prism** is a polyhedron with two parallel congruent faces, called bases, and all other faces that are parallelograms.

**Volume** is the number of cubic units needed to fill a space. Volume is measured in cubic units. The volume of a prism is found by multiplying the area of the base times the height.

### Finding the Area of the Triangle

**Find the height and width of a triangle base.**Look at the triangle and write down the base width and height. For example, your triangle might have a base of 8 cm and a height of 9 cm.

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- Keep in mind that you’re identifying the height of the
*triangle*, not the entire prism. - You can use either of the triangular bases, since they should have the same dimensions.

**Plug the numbers into the formula to find the triangular area.**Once you know the width and height of the triangle, put the numbers into the formula for calculating triangular area:

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- Area = 1/2 x width x height. You might also see it written as {V=(1/2)bh}

**Multiply 1/2 by width by height to get the area of the triangle.**In order to find the area of the triangular base for the prism, multiply the width by the height by 1/2. Remember to put the answer in square units because you’re calculating area.

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### Figuring the Volume of the Prism

**Plug the triangular area into the formula to find the volume of the prism.**The area of the triangle is 1 of the 2 numbers you need in order to find the prism’s volume. In the formula {V=Bh}, the triangular area is {B}.

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- To use the earlier example, the formula would be {V=36*h}.

**Identify the height of the prism and put it in the formula.**Now you need to find the height of the triangular prism, which is the length of 1 of its sides. For example, the prism may be 16 cm long. Place this number in the {h} place of the formula.

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- For example, your formula should now look like {V=36*16}.