ACT Math : Geometry

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #11 : Coordinate Geometry

The coordinates of the endpoints of , in the standard  coordinate plane, are  and . What is the -coordinate of the midpoint of ?

Possible Answers:

Correct answer:

Explanation:

To answer this question, we need to find the midpoint of .

To find how far the midpoint of a line is from each end, we use the following equation:

 and  are taken from the  value of the second point and  and  are taken from the  value of the first point. Therefore, for this data:

We can then solve:

Therefore, our midpoint is  units between each endpoint's  value and  unit between each endpoint's  value. To find out the location of the midpoint, we subtract the midpoint distance from the  point. (In this case it's the point .) Therefore:

So the midpoint is located at 

The question asked us what the -coordinate of this point was. Therefore, our answer is .

Example Question #11 : Coordinate Geometry

Following the line , what is the distance from the the point where  to the point where ?

Possible Answers:

Correct answer:

Explanation:

The first step is to find the y-coordinates for the two points we are using. To do this we plug our x-values into the equation. Where , we get , giving us the point . Where , we get , giving us the point .

We can now use the distance formula: .

Plugging in our points gives us 

Example Question #11 : Coordinate Geometry

Which of the following is the slope-intercept form of ?

Possible Answers:

Correct answer:

Explanation:

To answer this question, we must put the equation into slope-intercept form, meaning we must solve for . Slope-intercept form follows the format  where  is the slope and  is the intercept.

Therefore, we must solve the equation so that  is by itself. First we add  to both sides so that we can start to get  by itself:

Then, we must subtract  from both sides:

We then must divide each side by 

Therefore, the slope-intercept form of the original equation is .

Example Question #1 : Solid Geometry

If we have a regular (the triangles are equilateral) triangular prism of volume  and the side length of the triangle on either face is , what is the length of the prism? Write your answer in terms of a decimal rounded to the nearest hundredth.

Possible Answers:

Not enough information to decide.

Correct answer:

Explanation:

The volume of a triangular prism can be simply stated as V = A*L, where A is the area of the triangular face and L is the length. We have the volume already and we need to figure out the area of the triangle from the side length.

The area of a triangle is b*h/2, and we are given the base/side length: 3 in. We also have a formula for the height of an equilateral triangle, . Calculating the area of the triangle we get 2.5981 in^2, so now we just have to plug our numbers into the volume formula.

And that is the final answer.

Example Question #1 : Solid Geometry

Roberto has a swimming pool that is in the shape of a rectangular prism. His swimming pool is  meters wide,  meters long, and  meters deep. He needs to fill up the pool for summer, and his hose fills at a rate of  cubic meters per hour. How many hours will it take for Roberto to fill up the swimming pool?

Possible Answers:

Correct answer:

Explanation:

First, find the volume of the pool. For a rectangular prism, the formula for the volume is the following:

For the swimming pool,

 cubic meters

Now, because the hose only fills up  cubic meters per hour, divide the total volume by  to find how long it will take for the pool to fill.

It will take the pool  hours to fill by hose.

Example Question #1 : Solid Geometry

Matt baked a rectangular cake for his mom's birthday. The cake was  inches long,  inches wide, and  inches high. If he cuts the cake into pieces that are  inches long,  inches wide, and  inches high, how many pieces of cake can he cut?

Possible Answers:

Correct answer:

Explanation:

First, find the volume of the cake. For a rectangular prism,

Next, find the volume of each individual slice.

Now, divide the volume of the entire cake by the volume of the slice to get how many pieces of cake Matt can cut.

Example Question #2 : Solid Geometry

A cube has a surface area of . What is its volume?

Possible Answers:

Correct answer:

Explanation:

First, find the side lengths of the cube.

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

, where  is 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, recall that the volume of a cube is given by the following equation:

Example Question #3 : Solid Geometry

The volume of the right triangular prism is . Find the value of .

1

Possible Answers:

Correct answer:

Explanation:

The volume of a right triangular prism is given by the following equation:

Now, for the given question, the height is .

Since the area of the base is a right triangle, we can plug in the given values to find .

Example Question #1 : How To Find The Volume Of A Polyhedron

The tent shown below is in the shape of a triangular prism. What is the volume of this tent in cubic feet?

2

Possible Answers:

Correct answer:

Explanation:

The volume of a right triangular prism is given by the following equation:

Example Question #1 : How To Find The Volume Of A Polyhedron

The height of a box is twice its width and half its length. If the volume of the box is , what is the length of the box?

Possible Answers:

Correct answer:

Explanation:

For a rectangular prism, the formula for the volume is the following:

Now, we know that the height is twice its width. We can rewrite that as:

We also know that the height is half its length. That can be written as:

Now, we can plug in the values of the length, width, and height in terms of height to find the height.

The question wants to find the length of the box. Plug in the value of the height in the earlier equation we wrote earlier to represent the relatioinship between the height and the length.

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