PSAT Math : Plane Geometry

Study concepts, example questions & explanations for PSAT Math

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Example Questions

Example Question #2 : How To Find The Length Of The Diagonal Of A Hexagon

Regular hexagon  has side length 1.

Give the length of diagonal 

Possible Answers:

Correct answer:

Explanation:

The key is to examine  in thie figure below:

Hexagon_50

Each interior angle of a regular hexagon, including , measures , so it can be easily deduced by way of the Isosceles Triangle Theorem that . To find  we subtract  from  . Thus resullting in 

Also, by symmetry,

,

so ,

and  is a  triangle whose short leg  has length .

The long leg  of this  triangle measures  times the length of short leg , so .

Example Question #581 : Geometry

Hexagon

Note: Figure NOT drawn to scale.

The perimeter of the above hexagon is 888. Also, . Evaluate .

Possible Answers:

Insufficient information is given to answer the problem.

Correct answer:

Explanation:

The perimeter of the figure can be expressed in terms of the variables by adding:

Simplify and set :

Along with , we now have a system of equations to solve for  by adding:

 

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

Hexagon

Note: Figure NOT drawn to scale.

The perimeter of the above figure is 132. What is  ?

Possible Answers:

Correct answer:

Explanation:

The perimeter of the figure can be expressed in terms of the variables by adding:

Simplify and set :

Example Question #2 : Hexagons

Hexagon

Note: Figure NOT drawn to scale.

The perimeter of the above figure is 600. The ratio of  to  is . Evaluate 

Possible Answers:

Correct answer:

Explanation:

The perimeter of the figure can be expressed in terms of the variables by adding:

Simplify and set :

Since the ratio of  to  is equivalent to  - or

,

then 

and we can substitute as follows:

Example Question #2 : Hexagons

Hexagon1

Possible Answers:

190

210

180

200

170

Correct answer:

190

Explanation:

Hexagon2Hexagon3

Example Question #21 : Geometry

If a triangle has 180 degrees, what is the sum of the interior angles of a regular octagon?

Possible Answers:

Correct answer:

Explanation:

The sum of the interior angles of a polygon is given by  where  = number of sides of the polygon.  An octagon has 8 sides, so the formula becomes

Example Question #2 : How To Find An Angle In A Hexagon

In a rectangular hexagon, what is the meaure of each interior angle?

Possible Answers:

120 degrees

72 degrees

90 degrees

150 degrees

105 degrees

Correct answer:

120 degrees

Explanation:

The sum of the interior angles of a hexagon must equal 720 degrees. Because the hexagon is regular, all of the interior angles will have the same measure. A hexagon has six sides and six interior angles. Therefore, each angle measures.

Example Question #1 : How To Find An Angle In A Hexagon

Hexagon

Note:Figure NOT drawn to scale.

Refer to the above figure. Evaluate .

Possible Answers:

Correct answer:

Explanation:

The sum of the degree measures of the angles of a (six-sided) hexagon, is

We can solve for  in the equation

Example Question #581 : Geometry

Hexagon

Note: Figure NOT drawn to scale.

Refer to the above figure. Evaluate .

Possible Answers:

Correct answer:

Explanation:

The sum of the degree measures of the angles of a (six-sided) hexagon, is

We can solve for  in the equation

 

Example Question #582 : Geometry

Three angles of a hexagon measure . The other three angles are congruent to one another. What is the measure of each of the latter three angles?

Possible Answers:

This hexagon cannot exist.

Correct answer:

Explanation:

The sum of the degree measures of the angles of a (six-sided) hexagon, is

Let  be the common measure of the three congruent angles in question. We can solve for  in the equation

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