ACT Math : Solid Geometry

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #11 :Other Polyhedrons

金字塔被放置在一个多维数据集沙re a base and height. If the surface area of the cube is, what is the volume of the pyramid, in square feet?

Possible Answers:

Correct answer:

Explanation:

First, we need to find the length of a side for the cube.

Recall that the surface area of the cube is given by the following equation:

, whereis the length of a side.

Plugging in the surface area given by the equation, we can then find the side length of the cube.

Now, because the pyramid and the cube share a base, we know that the pyramid must be a square pryamid.

Recall how to find the volume of a pyramid:

Now, since the pyramid is the same height as the cube, the height of the pyramid is also.

Example Question #11 :Solid Geometry

In cubic feet, find the volume of the pentagonal prism illustrated below. The pentagon has an area of, and the prism has a height of.

4

Possible Answers:

Correct answer:

Explanation:

For any prism, the volume is given by the following equation:

The question gives us the area of the base and the height.

Example Question #12 :Solid Geometry

If the side lengths of a cube are tripled, what effect will it have on the volume?

Possible Answers:

The volume will betimes as large.

The volume will betimes as large.

The volume will betimes as large.

The volume will betimes as large.

Correct answer:

The volume will betimes as large.

Explanation:

Start by taking a cube that is. The volume of this cube is.

Next, triple the sides of this cube so that it becomes. The volume of this cube is.

The volume of the new cube istimes as large as the original.

Example Question #921 :Act Math

The surface area of a cylinder is given by, whereis the radius andis the height. If a cylinder has a surface area ofand a height of, what is its radius?

Possible Answers:

Correct answer:

Explanation:

The fastest way to solve this problem is to plug all of the answer choices in forand look for an output of.

Alternatively, one could set the surface area formula equal to(knowing that), but this would require solving a quadratic.

Rearranging this we get

Now factoring out awe get:

Since we cannot have a negative length our answer is.

Example Question #14 :Solid Geometry

If a half cylinder with a height of 5 and semicircular bases with a radius of 2, what is the surface area?

Possible Answers:

Correct answer:

Explanation:

The surface area of the half cylinder will consist of the lateral area and the base area.

There are three parts to the surface area:

Rectangular region, semi-circular bases of the half cylinder, and outer face of the cylinder.

The cross section of the half cylinder is a rectangle. Find the area of the rectangle. The diameter of the semicircle represents the width of the rectangle, which is double the radius. The length of the rectangle is the height of the cylinder.

Next, find the area of a semicircular bases.

Since there are two semicircular bases of the semi-cylinder, the total area of the semicircular bases is.

Find the area of the outer region. The area of the outer region is the half circumference multiplied by the height of the cylinder.

Sum the areas of the rectangle, the two circular bases, and the outer region to find the lateral area.

Example Question #1 :How To Find The Length Of An Edge Of A Cube

Our backyard pool holds 10,000 gallons. Its average depth is 4 feet deep and it is 10 feet long. If there are 7.48 gallons in a cubic foot, how wide is the pool?

Possible Answers:

3.3.ft

100 ft

3.0 ft

133 ft

7.48 ft

Correct answer:

3.3.ft

Explanation:

There are 7.48 gallons in cubic foot. Set up a ratio:

1 ft3./ 7.48 gallons = x cubic feet / 10,000 gallons

Pool Volume = 10,000 gallons = 10,000 gallons * (1 ft3./ 7.48 gallons) = 1336.9 ft3.

Pool Volume = 4ft x 10 ft x WIDTH = 1336.9 cubic feet

Solve for WIDTH:

4 ft x 10 ft x WIDTH = 1336.9 cubic feet

WIDTH = 1336.9 / (4 x 10) = 33.4 ft

Example Question #1 :How To Find The Length Of An Edge Of A Cube

A cube has a volume of 64cm3.. What is the area of one side of the cube?

Possible Answers:

16cm2

16cm

16cm3.

4cm2

4cm

Correct answer:

16cm2

Explanation:

多维数据集的容积是64厘米3., making the length of one edge 4cm (4 * 4 * 4 = 64).

So the area of one side is 4 * 4 = 16cm2

Example Question #11 :Solid Geometry

A cube as the volume of.

Find the length of a side of this cube.

Possible Answers:

Correct answer:

Explanation:

The formula to find the volume of the cube is

Since we know the volume, we can set up the equation

Example Question #2 :Cubes

A cube has a surface area of, what is the length of the side of the cube? (If necessary, round to the nearest hundredth.)

Possible Answers:

Correct answer:

Explanation:

To find the length of the side of a square given the surface area, use the surface area formula and solve for:

, now divide both sides by 6
, now square root both sides
.

Example Question #3 :Cubes

A certain cubic box when unfolded and laid flat on a table covers exactlysquare units of space. What is the width of the box, in units?

Possible Answers:

Correct answer:

Explanation:

To find the length of the edge of a cube from its surface area, remember that, whereis the length of a side.

So, the box isunits long.

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