High School Math : How to find the perimeter of a polygon

Study concepts, example questions & explanations for High School Math

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Example Questions

Example Question #1 : Geometry

What is the perimeter of a regular hendecagon with a side length of 32?

Possible Answers:

\(\displaystyle 334\)

\(\displaystyle 320\)

\(\displaystyle 384\)

\(\displaystyle 352\)

Correct answer:

\(\displaystyle 352\)

Explanation:

To find the perimeter of a regular hendecagon you must first know the number of sides in a hendecagon is 11.

When you know the number of sides of a regular polygon to find the perimeter you must multiply the side length by the number of sides.

In this case it is \(\displaystyle 11*32=352\).

The answer for the perimeter is \(\displaystyle 352\)

Example Question #1 : How To Find The Perimeter Of A Polygon

Polygon

All segments of the polygon meet at right angles (90 degrees). The length of segment \overline{AB}\(\displaystyle \overline{AB}\) is 10. The length of segment \overline{BC}\(\displaystyle \overline{BC}\) is 8. The length of segment \overline{DE}\(\displaystyle \overline{DE}\) is 3. The length of segment \overline{GH}\(\displaystyle \overline{GH}\) is 2.

Find the perimeter of the polygon.

Possible Answers:

\dpi{100} \small 42\(\displaystyle \dpi{100} \small 42\)

\dpi{100} \small 46\(\displaystyle \dpi{100} \small 46\)

\dpi{100} \small 44\(\displaystyle \dpi{100} \small 44\)

\dpi{100} \small 40\(\displaystyle \dpi{100} \small 40\)

\dpi{100} \small 48\(\displaystyle \dpi{100} \small 48\)

Correct answer:

\dpi{100} \small 46\(\displaystyle \dpi{100} \small 46\)

Explanation:

The perimeter of the polygon is 46. Think of this polygon as a rectangle with two of its corners "flipped" inwards. This "flipping" changes the area of the rectangle, but not its perimeter; therefore, the top and bottom sides of the original rectangle would be 12 units long \dpi{100} \small (10+2=12)\(\displaystyle \dpi{100} \small (10+2=12)\). The left and right sides would be 11 units long \dpi{100} \small (8+3=11)\(\displaystyle \dpi{100} \small (8+3=11)\). Adding all four sides, we find that the perimeter of the recangle (and therefore, of this polygon) is 46.

Example Question #2 : Geometry

What is the perimeter of a regular nonagon with a side length of \(\displaystyle 15\)?

Possible Answers:

\(\displaystyle 120\)

\(\displaystyle 150\)

\(\displaystyle 135\)

\(\displaystyle 105\)

Correct answer:

\(\displaystyle 135\)

Explanation:

To find the perimeter of a regular polygon, we take the length of each side, \(\displaystyle l\), and multiply it by the number of sides, \(\displaystyle s\).

\(\displaystyle P=s*l\)

In a nonagon the number of sides is \(\displaystyle 9\), and in this example the side length is \(\displaystyle 15\).

\(\displaystyle P=9*15=135\)

The perimeter is \(\displaystyle 135\).

 

Example Question #2 : Geometry

Find the perimeter of the following octagon:

20

Possible Answers:

\(\displaystyle 56\ m\)

 

\(\displaystyle 96\ m\)

\(\displaystyle 76\ m\)

\(\displaystyle 66\ m\)

\(\displaystyle 86\ m\)

Correct answer:

\(\displaystyle 96\ m\)

Explanation:

The formula for the perimeter of an octagon is \(\displaystyle P = 8(side)\).

Plugging in our values, we get:

\(\displaystyle P = 8(12\ m)\)

\(\displaystyle P = 96\ m\)

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