Common Core: 8th Grade Math : Grade 8

Study concepts, example questions & explanations for Common Core: 8th Grade Math

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Example Questions

Example Question #2 : How To Find The Volume Of A Cylinder

Find the volume, in cubic inches, of a cylinder that has a radius of  inches and a height of  inches.

Possible Answers:

 

 

 

 

Correct answer:

 

Explanation:

The formula to find the volume of a cylinder is .

Now, plug in the given numbers into this equation.

 

Example Question #731 : Geometry

Find the volume of the cylinder if the circular base has an area of , and the height of the cylinder is also 

Possible Answers:

Correct answer:

Explanation:

Write the formula for volume of a cylinder.

Remember that area of a circle is  

Since the area of the circle is known, substitute the area into the formula.

Example Question #491 : Grade 8

A car dealership wants to fill a large spherical advertising ballon with helium. It can afford to buy 1,000 cubic yards of helium to fill this balloon. What is the greatest possible diameter of that balloon (nearest tenth of a yard)?

Possible Answers:

Correct answer:

Explanation:

The volume of a sphere, given its radius, is 

Set , solve for , and double that to get the diameter.

The diameter is twice this, or 12.4 yards.

Example Question #492 : Grade 8

The diameter of a sphere is . Give the volume of the sphere in terms of .

Possible Answers:

Correct answer:

Explanation:

The diameter of a sphere is  so the radius of the sphere would be 

 

The volume enclosed by a sphere is given by the formula:

 

 

 

Example Question #493 : Grade 8

A spherical balloon has a diameter of 10 meters. Give the volume of the balloon.

Possible Answers:

Correct answer:

Explanation:

The volume enclosed by a sphere is given by the formula:

where  is the radius of the sphere. The diameter of the balloon is 10 meters so the radius of the sphere would be meters. Now we can get:

 

Example Question #3 : Volume Of A Three Dimensional Figure

The volume of a sphere is 1000 cubic inches. What is the diameter of the sphere.

Possible Answers:

Correct answer:

Explanation:

The volume of a sphere is:

 

Where is the radius of the sphere. We know the volume and can solve the formula for :

 

 inches

 

So we can get:

 

Example Question #621 : Geometry

A sphere has a diameter of  inches. What is the volume of this sphere?

Possible Answers:

 

 

 

 

Correct answer:

 

Explanation:

To find the volume of a sphere, use the following formula:

, where  is the radius of the sphere.

Now, because we are given the diameter of the sphere, divide that value in half to find the radius.

 

Now, plug this value into the volume equation.

  

Example Question #2 : How To Find The Volume Of A Sphere

What is the volume of a sphere with a diameter of ?

Possible Answers:

Correct answer:

Explanation:

Write the formula for the volume of the sphere.

The radius is half the diameter, which is five.  Substitute the value.

Example Question #494 : Grade 8

A cone has height 18 inches; its base has radius 4 inches. Give its volume in cubic feet (leave in terms of  )

Possible Answers:

Correct answer:

Explanation:

Convert radius and height from inches to feet by dividing by 12:

Height: 18 inches =  feet

Radius: 4 inches = 

The volume of a cone is given by the formula

Substitute :

Example Question #495 : Grade 8

A cone has height 240 centimeters; its base has radius 80 centimeters. Give its volume in cubic meters.

Possible Answers:

Correct answer:

Explanation:

Convert both dimensions from centimeters to meters by dividing by 100:

Height: 240 centimeters =   meters.

Radius: 80 centimeters =  meters.

Substitute  in the volume formula:

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