## Subjects

# The perimeter of a polygon

How many straight sides does a pentagon have?

## The perimeter of a polygon

What is this? It looks like a honeycomb. What a strange pattern. One, two, three, four, five, six straight sides! A shape with six straight sides is one of the many-sided figures in geometry.

There are several of them. Three straight sides makes a shape called a triangle. Four straight sides makes a quadrilateral, such as a square. Five sides makes a pentagon, Six sides: a hexagon. Then there are heptagons, octagons, nonagons, and more.

The common name for a figure with three or more straight sides is a polygon. Poly comes from the Greek word for many and gon means corner. Many corners - many cornered figures. If all sides have the same length and.. ..all interior angles are equal it is a.. ..regular polygon. The perimeter of a regular polygon can be calculated like this: The length of one of the sides multiplied by the number of sides.

A pentagon - a five sided figure with sides of 2 centimetres.. ..has the perimeter 2 centimetres times 5. That’s 10 centimetres. For all regular polygons, the perimeter is the length of one side times the number of sides. If all the sides don’t have the same length —if the polygon is irregular —then we must measure all of the sides to be able to calculate the perimeter. But the honeycomb that Lina found consists of regular hexagons.

She only needs to measure one side and multiply that length by six to get the perimeter of one of the many small parts of the honeycomb. Lina measures one of the sides. She finds the length is 3 millimetres. So what then is the perimeter of the hexagon? Can you help Lina?