Other Quadrilaterals - ACT Math

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Question

The interior angles of a quadrilateral are , , , and . What is the measure of the smallest angle of the quadrilateral?

Answer

In order to solve this problem we need the following key piece of knowledge: the interior angles of a quadrilateral add up to 360 degrees. Now, we can write the following equation:

When we combine like terms, we get the following:

We will need to subtract 71 from both sides of the equation:

Now, we will divide both sides of the equation by 17.

We now have a value for the x-variable; however, the problem is not finished. The question asks for the measure of the smallest angle. We know that the smallest angle will be one of the following:

or

In order to find out, we will substitute 17 degrees for the x-variable.

Because 51 degrees is less than 71 degrees, the measure of the smallest angle is the following:

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Question

Q6

bisects . If then, in degrees, what is the value of ?

Answer

A rectangle has two sets of parallel sides with all angles equaling 90 degrees.

Since bisects into two equal parts, this creates an isosceles triangle .

Therefore . The sum of the angles in a triangle is 180 degrees.

Therefore

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Question

Q8

The rhombus above is bisected by two diagonals.

If and then, in degrees, what is the value of the ?

Note: The shape above may not be drawn to scale.

Answer

A rhombus is a quadrilateral with two sets of parallel sides as well as equal opposite angles. Since the lines drawn inside the rhombus are diagonals, and are each bisected into two equal angles.

Therefore, , which creates a triangle in the upper right quadrant of the kite. The sum of angles in a triangle is 180 degreees.

Thus,

Since is only half of ,

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Question

Q10

If and , then, in degrees, what is the value of ?

Note: The figure may not be drawn to scale.

Answer

In a rhombus, opposite angles are equal to each other. Therefore we can set and equal to one another and solve for :

Therefore,

A rhombus, like any other quadrilateral, has a sum of angles of 360 degrees.

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Question

The sides of rectangle A measure to , , , and . Rectangle B is similar to Rectangle A. The shorter sides of rectangle B measure each. How long are the longer sides of Rectangle B?

Answer

In similar rectangles, the ratio of the sides must be equal.

To solve this question, the following equation must be set up:

, using as the variable for the missing side.

We then must cross multiply, which leaves us with:

Lastly, we divide both sides by 8 to solve for the missing side:

Therefore, the longer sides of the rectangle are each .

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Question

Suppose a rectangle has side lengths of 7 and 3. Another rectangle has another set of side lengths that are 8 and 4. Are these similar rectangles, and why?

Answer

Set up the proportion to determine if the ratios of both rectangles are equal.

If they are, then they are similar.

These are not similar rectangles since their ratios are not the same.

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Question

Jane plans to re-tile her kitchen with tiles that have a length of inches and a width of inches wide. If her kitchen measures feet by feet, how many tiles will she need?

Answer

When attempting to solve how many pieces of a particular object you need to cover a certain area, always make sure that your units of measurement (for the object and for the area you are covering) are the same. In the case of this question, the units of measurement are different, so you must first convert all measurements to use the same unit.

Since the tiles being used to cover the area are measured in inches, convert all units given to inches:

Length: feet inches

Width: feet inches

Then, find the area of the entire space you are covering. Since the space is rectangular (this can be assumed since only length and width are given as measurements), multiply the length and width to find the total area: square inches.

Next, find the area of each of the tiles: square inches. Divide the total area of the space by the area of each of your tiles: . In cases where you are covering a certain area with an object, always round up if you have a decimal (no matter how small), because you cannot simply buy of a tile.

The answer is .

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Question

Vikram is looking at a scale drawing of a room he is building. The drawing is of a rectangle that measures inches by inches. If he knows the length of the longer side of the room will measure feet, what is the area of the room?

Answer

When solving such problems, always make sure that your units of measurement are all the same. In the case of this problem, you must convert feet to inches. Multiply 30 by 12 in order to get its equivalent in inches.

We know that the 30 feet corresponds with the side of the drawing that is 18 inches because it is stated that the longest side will be 30 feet. Divide 360 by 18 in order to find the ratio of the actual size of the room to the measurements on the drawing

This means that the actual measurements of the room are 20 times the measurements of the drawing. Multiply 20 times 12 in order to find the measurement of the shorter side in inches.

Divide both the 360 and 240 by 12 to convert the measurements back into feet.

Then multiply the results to get the final answer.

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Question

If a trapezoid has base lengths of and and a height of , what is its area?

Answer

Use the formula for area of a trapezoid:

Where is the area, and are the lengths of the two bases, and is the height.

In this case:

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Question

A parallelogram has a side length of , a height of , and a base length of . What is its area?

Answer

Use the formula for area of a parallelogram:

Where is the area, is the base length, and is the height.

In this case:

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Question

Q12

In the parallelogram above, and . What is the length of the diagonal ?

Answer

In a parallelogram, the two diagonals bisect each other at their centers. Therefore, . To find , we set them equal to one another and solve.

Plugging this value back into both equations, then adding those values together, gives us our answer of .

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Question

A square has a length of . What must be the length of the diagonal?

Answer

A square with a length of indicates that all sides are since a square has 4 equal sides. Use the Pythagorean Theorem to solve for the diagonal.

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Question

If the rectangle has side lengths of and , what is the diagonal of the rectangle?

Answer

Use the Pythagorean Theorem to solve for the diagonal.

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Question

Q9

Find the perimeter of the rhombus above.

Answer

By definition, a rhombus is a quadrilateral with four equal sides whose angles do not all equal 90 degrees. To find the perimeter, we must find the values of x and y. In order to do so, we must set up a system of equations where we set two sides equal to each other. Any two sides can be used to create these systems.

Here is one example:

Eq. 1

Eq. 2

Now we plug into the first equation to find the value of :

Plugging these values into any of the three equations will give us the length of one side equaling 11.

Since there are four sides, .

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Question

Find the length of a rectangle if the area is , and the width is .

Answer

Write the formula to solve the area of a rectangle.

Substitute the dimension and area to solve for the length.

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Question

If the perimeter of a square is and the area is , what is the side length of the square?

Answer

The square has 4 equal sides. Let's assume a side is .

Each side of the square has a length of .

The area of the square is:

Substitute into the area to solve for .

Since one side of the square is , substitute the value of to determine the length of the square side.

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Question

Find the side of a square if the area is .

Answer

The area of a square is:

Substitute the area and solve for the side.

The quantity inside the square root may not be factorized in attempt to eliminate the square root!

The side length of the square is:

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Question

A homeowner wants to set up a rectangular enclosure for his dog. The plot of land that the enclosure will enclose measures by . What is the length in feet of chain link fence the owner will need to create a fence around the enclosure?

Answer

To answer this question, we must find the perimeter of the fence the homeowner is wanting to create.

To find the perimeter of a rectangle, we multiply the length by two, multiply the width by two, and add these two numbers together. The equation can be represented as this:

We must then plug in our values of and given to us for the length and width.

So for this data:

Therefore, the amount of fencing needed to fully surround the dog's enclosure is .

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