Intermediate Geometry : Plane Geometry

Study concepts, example questions & explanations for Intermediate Geometry

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Example Questions

Example Question #1 : How To Find The Length Of The Side Of A Pentagon

A regular pentagon has an area of  square units and an apothem measurement of . Find the length of one side of the pentagon. 

Possible Answers:

Correct answer:

Explanation:

A regular pentagon must have five equivalent sides and five equivalent interior angles. Regular pentagons can be divided up into five equivalent interior triangles, where the base of the triangle is a side length and the height of the triangle is the apothem. This problem provides the total area for the pentagon. 

Therefore, you must work backwards using the area formula: , where the base is equal to the length of one side of the triangle and the height of the triangle is the measurement of the apothem. However, this will only provide the measurement for one of the five interior triangles, thus you first need to divide the total area by 

The solution is:



So, area of one of the five interior triangles is equal to: 

Now, apply the area formula: 





Example Question #2 : How To Find The Length Of The Side Of A Pentagon

Pentagon_series_vt_custom

The pentagon shown above has been divided into a top portion with two equivalent right triangles and a bottom rectangular portion. Find the length of side 

Possible Answers:

Correct answer:

Explanation:

To solve this problem notice that the area is provided for the bottom rectangular portion of the pentagon. Therefore, work backwards using the area formula: 





Example Question #2 : How To Find The Length Of The Side Of A Pentagon

A regular pentagon has a perimeter of . Find the length of one side of the pentagon. 

Possible Answers:

Correct answer:

Explanation:

By definition a regular pentagon must have five equivalent sides and five equivalent interior angles. Since this problem provides the measurement for the total perimeter of the pentagon, work backwards using the formula: 

, where  the length of one side of the pentagon. 





Check:

Example Question #2 : How To Find The Length Of The Side Of A Pentagon

A regular pentagon has an area of  square units and an apothem measurement of . Find the length of one side of the pentagon. 

Possible Answers:

Correct answer:

Explanation:

A regular pentagon must have five equivalent sides and five equivalent interior angles. Regular pentagons can be divided up into five equivalent interior triangles, where the base of the triangle is a side length and the height of the triangle is the apothem. This problem provides the total area for the pentagon. 

Therefore, you must work backwards using the area formula: , where the base is equal to the length of one side of the triangle and the height of the triangle is the measurement of the apothem. However, this will only provide the measurement for one of the five interior triangles, thus you first need to divide the total area by 

The solution is:



So, area of one of the five interior triangles is equal to: 

Now, apply the area formula: 





Example Question #1 : How To Find The Length Of The Side Of A Pentagon

A regular pentagon has a perimeter of . Find the length of one side of the pentagon.

Possible Answers:

Correct answer:

Explanation:

By definition a regular pentagon must have five equivalent sides and five equivalent interior angles. Since this problem provides the measurement for the total perimeter of the pentagon, work backwards using the formula: 

, where  the length of one side of the pentagon. 



Example Question #1 : How To Find The Length Of The Side Of A Pentagon

A regular pentagon has an area of  square units and an apothem measurement of . Find the length of one side of the pentagon. 

Possible Answers:

Correct answer:

Explanation:

A regular pentagon must have five equivalent sides and five equivalent interior angles. Regular pentagons can be divided up into five equivalent interior triangles, where the base of the triangle is a side length and the height of the triangle is the apothem. This problem provides the total area for the pentagon. 

Therefore, you must work backwards using the area formula: , where the base is equal to the length of one side of the triangle and the height of the triangle is the measurement of the apothem. However, this will only provide the measurement for one of the five interior triangles, thus you first need to divide the total area by 

The solution is:



So, area of one of the five interior triangles is equal to: 

Now, apply the area formula: 





Example Question #1 : How To Find The Length Of The Side Of A Pentagon

Pentagon_series_vt_custom

The pentagon shown above has been divided into a top portion with two equivalent right triangles and a bottom rectangular portion. Find the length of side 

Possible Answers:

Correct answer:

Explanation:

To solve this problem notice that the area is provided for the bottom rectangular portion of the pentagon. Therefore, work backwards using the area formula: 







CHECK:

Example Question #761 : Intermediate Geometry

A regular pentagon has a perimeter of . Find the length of one side of the pentagon. 

Possible Answers:

Correct answer:

Explanation:

A regular pentagon must have five equivalent sides and five equivalent interior angles.

This problem provides the measurement for the total perimeter of the pentagon, work backwards using the formula: 

, where  the length of one side of the pentagon. 



Example Question #22 : Pentagons

A regular pentagon has an area of  square units and an apothem measurement of . Find the length of one side of the pentagon.

Possible Answers:

Correct answer:

Explanation:

A regular pentagon must have five equivalent sides and five equivalent interior angles. Regular pentagons can be divided up into five equivalent interior triangles, where the base of the triangle is a side length and the height of the triangle is the apothem. This problem provides the total area for the pentagon. 

Therefore, you must work backwards using the area formula: , where the base is equal to the length of one side of the triangle and the height of the triangle is the measurement of the apothem. However, this will only provide the measurement for one of the five interior triangles, thus you first need to divide the total area by 

The solution is:



So, area of one of the five interior triangles is equal to: 

Now, apply the area formula: 





Example Question #31 : Pentagons

If a regular pentagon has an area of  and an apothem length of , what is the length of a side of the pentagon?

Possible Answers:

Correct answer:

Explanation:

Recall how to find the area of a regular pentagon:

Now, the perimeter of a regular pentagon can be found by multiplying the side length by :

Substitute this into the equation for the area.

Now, rearrange the equation to solve for the side length.

Plug in the given area and apothem to solve for the side length of the pentagon.

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