PSAT Math : Quadrilaterals

Study concepts, example questions & explanations for PSAT Math

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Example Questions

Example Question #2 : How To Find If Rectangles Are Similar

Rectangles

Note: Figure NOT drawn to scale.

In the above figure,

.

.

Give the area of .

Possible Answers:

Insufficient information is given to determine the area.

Correct answer:

Explanation:

Corresponding sidelengths of similar polygons are in proportion, so

, so

We can use the Pythagorean Theorem to find :

The area of  is 

 

Example Question #1 : How To Find If Rectangles Are Similar

Rectangles

Note: Figure NOT drawn to scale.

In the above figure,

.

.

Give the area of Polygon .

Possible Answers:

Correct answer:

Explanation:

Polygon  can be seen as a composite of right  and , so we calculate the individual areas and add them.

The area of  is half the product of legs  and :

 

Now we find the area of . We can do this by first finding  using the Pythagorean Theorem:

The similarity of  to  implies

so

The area of  is the product of  and :

 

Now add: , the correct response.

Example Question #1 : How To Find If Rectangles Are Similar

Rectangles

Note: Figure NOT drawn to scale.

Refer to the above figure. 

 and .

What percent of  has been shaded brown ?

Possible Answers:

Insufficient information is given to answer the problem.

Correct answer:

Explanation:

 and , so the similarity ratio of  to  is 10 to 7. The ratio of the areas is the square of this, or 

or 

Therefore,  comprises  of , and the remainder of the rectangle - the brown region - is 51% of .

Example Question #313 : Plane Geometry

Rectangles

Note: figure NOT drawn to scale.

Refer to the above figure. 

.

Give the area of .

.

Possible Answers:

Correct answer:

Explanation:

, so the sides are in proportion - that is,

Set 

 and solve for :

 has area 

Example Question #1 : Rectangles

A rectangle has a width of 2x. If the length is five more than 150% of the width, what is the perimeter of the rectangle?

Possible Answers:

6x2 + 5

10(x + 1)

5x + 10

5x + 5

6x2 + 10x

Correct answer:

10(x + 1)

Explanation:

Given that w = 2x and l = 1.5w + 5, a substitution will show that l = 1.5(2x) + 5 = 3x + 5.  

P = 2w + 2l = 2(2x) + 2(3x + 5) = 4x + 6x + 10 = 10x + 10 = 10(x + 1)

Example Question #11 : Rectangles

Garden

Note: Figure NOT drawn to scale

Refer to the above figure, which shows a rectangular garden (in green) surrounded by a dirt path (in orange). The dirt path is seven feet wide throughout. Which of the following polynomials gives the perimeter of the garden in feet?

Possible Answers:

Correct answer:

Explanation:

The length of the garden, in feet, is  feet less than that of the entire lot, or 

;

The width of the garden, in feet, is  less than that of the entire lot, or 

.

The perimeter, in feet, is twice the sum of the two:

Example Question #11 : Rectangles

 

Garden

Note:  Figure NOT drawn to scale

Refer to the above figure, which shows a square garden (in green) surrounded by a dirt path (in orange) eight feet wide throughout. What is the perimeter of the garden?

Possible Answers:

Correct answer:

Explanation:

The inner square, which represents the garden, has sidelength  feet, so its perimeter is four times this:

 feet.

Example Question #1 : How To Find The Perimeter Of A Rectangle

Farmer Dave has a rectangular field that is 50 yards wide and 40 yards long. He wants to enclose the field with a wire fence. How much wire does Farmer Dave need?

Possible Answers:

210 yards

180 yards

200 yards

160 yards

170 yards

Correct answer:

180 yards

Explanation:

To solve this problem, find the perimeter of the rectangle. There are two sides that each measure 50 yards and two sides that each measure 40 yards. Together these four sides measure 180 yards.

Example Question #1 : Rectangles

A rectangular garden has an area of . Its length is  meters longer than its width. How much fencing is needed to enclose the garden?

Possible Answers:

Correct answer:

Explanation:

We define the variables as  and .

We substitute these values into the equation for the area of a rectangle and get

 or 

Lengths cannot be negative, so the only correct answer is . If , then

Therefore, .

Example Question #4 : Quadrilaterals

A contractor is going to re-tile a rectangular section of the kitchen floor. If the floor is 6ft x 3ft, and he is going to use square tiles with a side of 9in. How many tiles will be needed?

 

                 

 

Possible Answers:

24

2

40

32

Correct answer:

32

Explanation:

We have to be careful of our units. The floor is given in feet and the tile in inches. Since the floor is 6ft x 3ft. we can say it is 72in x 36in, because 12 inches equals 1 foot. If the tiles are 9in x 9in we can fit 8 tiles along the length and 4 tiles along the width. To find the total number of tiles we multiply 8 x 4 = 32. Alternately we could find the area of the floor (72 x 36, and divide by the area of the tile 9 x 9)

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