GED Math : Geometry and Graphs

Study concepts, example questions & explanations for GED Math

varsity tutors app store varsity tutors android store

Example Questions

Example Question #124 : 3 Dimensional Geometry

Cone_1

Give the total surface area of the above cone to the nearest square meter.

Possible Answers:

Correct answer:

Explanation:

The base is a circle with radius , and its area can be calculated using the area formula for a circle:

 square meters.

To find the lateral area, we need the slant height of the cone. This can be found by way of the Pythagorean Theorem. Treating the height  and the radius  as the legs and slant height  as the hypotenuse, calculate:

 meters.

The formula for the lateral area can be applied now:

Add the base and the lateral area to obtain the total surface area:

.

This rounds to 186 square meters.

Example Question #125 : 3 Dimensional Geometry

A water tank takes the shape of a closed cylinder whose exterior has a height of 40 feet and a base with radius 15 feet; the tank is three inches thick throughout. To the nearest hundred, give the surface area of the interior of the tank in square feet.

Use 3.14 for .

Possible Answers:

Correct answer:

Explanation:

Three inches is equal to 0.25 feet, so the height of the interior of the tank is 

 feet.

The radius of the interior of the tank is 

 feet.

The surface area of the interior of the tank can be determined by using this formula:

,

which rounds to 5,000 square feet.

Example Question #5 : Faces And Surface Area

Cone_1

Above is a diagram of a conic tank that holds a city's water supply. 

The city wishes to completely repaint the exterior of the tank - sides and base. The paint it wants to use covers 40 square meters per gallon. Also, to save money, the city buys the paint in multiples of 25 gallons. 

How many gallons will the city purchase in order to paint the tower?

Possible Answers:

Correct answer:

Explanation:

The surface area of a cone with radius  and slant height  is calculated using the formula .

Substitute 35 for  and 100 for  to find the surface area in square meters:

 square meters.

The paint covers 40 square meters per gallon, so the city needs

 gallons of paint. 

Since the city buys the paint in multiples of 25 gallons, it will need to buy the next-highest multiple of 25, or 375 gallons.

Example Question #131 : 3 Dimensional Geometry

A regular octahedron has eight congruent faces, each of which is an equilateral triangle. 

A given octahedron has edges of length three inches. Give the total surface area of the octahedron.

Possible Answers:

Correct answer:

Explanation:

The area of an equilateral triangle is given by the formula

.

Since there are eight equilateral triangles that comprise the surface of the octahedron, the total surface area is 

.

Substitute :

 square inches.

Example Question #1645 : Ged Math

A regular icosahedron has twenty congruent faces, each of which is an equilateral triangle. 

A given regular icosahedron has edges of length two inches. Give the total surface area of the icosahedron.

Possible Answers:

Correct answer:

Explanation:

The area of an equilateral triangle is given by the formula

.

Since there are twenty equilateral triangles that comprise the surface of the icosahedron, the total surface area is 

.

Substitute :

  square inches.

Example Question #132 : 3 Dimensional Geometry

A regular tetrahedron has four congruent faces, each of which is an equilateral triangle. 

A given tetrahedron has edges of length five inches. Give the total surface area of the tetrahedron.

Possible Answers:

Correct answer:

Explanation:

The area of an equilateral triangle is given by the formula

.

Since there are four equilateral triangles that comprise the surface of the tetrahedron, the total surface area is 

.

Substitute :

 square inches.

Example Question #1651 : Ged Math

A cube has a height of 9cm.  Find the surface area. 

Possible Answers:

Correct answer:

Explanation:

To find the surface area of a cube, we will use the following formula:

where l is the length, and w is the width of the cube.

Now, we know the height of the cube is 9cm. Because it is a cube, all lengths, widths, and heights are the same. Therefore, the length and the width are also 9cm.

Knowing this, we can substitute into the formula. We get

Example Question #1652 : Ged Math

A sphere has a radius of 7in.  Find the surface area.

Possible Answers:

Correct answer:

Explanation:

To find the surface area of a sphere, we will use the following formula:

where r is the radius of the sphere.

Now, we know the radius of the sphere is 7in. 

So, we can substitute into the formula. We get

Example Question #681 : Geometry And Graphs

Find the surface area of a cube with a length of 12in.

Possible Answers:

Correct answer:

Explanation:

To find the surface area of a cube, we will use the following formula:

where l is the length, and w is the width of the cube.

Now, we know the length of the cube is 12in. Because it is a cube, all sides are equal. Therefore, the width is also 12in. So, we can substitute. We get

Example Question #1653 : Ged Math

A cube has a height of 8cm. Find the surface area. 

Possible Answers:

Correct answer:

Explanation:

To find the surface area of a cube, we will use the following formula:

where l is the length, and w is the width of the cube.

Now, we know the height of the cube is 8cm. Because it is a cube, all lengths, widths, and heights are the same. Therefore, the length and the width are also 8cm.

Knowing this, we can substitute into the formula. We get

Learning Tools by Varsity Tutors