All PSAT Math Resources
Example Questions
Example Question #12 : Squares
When the side of a certain square is increased by 2 inches, the area of the resulting square is 64 sq. inches greater than the original square. What is the length of the side of the original square, in inches?
15
18
17
16
14
15
Let x represent the length of the original square in inches. Thus the area of the original square is x2. Two inches are added to x, which is represented by x+2. The area of the resulting square is (x+2)2. We are given that the new square is 64 sq. inches greater than the original. Therefore we can write the algebraic expression:
x2 + 64 = (x+2)2
FOIL the right side of the equation.
x2 + 64 = x2 + 4x + 4
Subtract x2 from both sides and then continue with the alegbra.
64 = 4x + 4
64 = 4(x + 1)
16 = x + 1
15 = x
Therefore, the length of the original square is 15 inches.
If you plug in the answer choices, you would need to add 2 inches to the value of the answer choice and then take the difference of two squares. The choice with 15 would be correct because 172 -152 = 64.
Example Question #622 : Geometry
If the area of a square is 25 inches squared, what is the perimeter?
10
Not enough information
20
15
25
20
The area of a square is equal to length times width or length squared (since length and width are equal on a square). Therefore, the length of one side is or The perimeter of a square is the sum of the length of all 4 sides or
Example Question #621 : Geometry
What is the length of the diagonal of a rectangle that is 3 feet long and 4 feet wide?
The diagonal of the rectangle is equivalent to finding the length of the hypotenuse of a right triangle with sides 3 and 4. Using the Pythagorean Theorem:
Therefore the diagonal of the rectangle is 5 feet.
Example Question #622 : Geometry
The length and width of a rectangle are in the ratio of 3:4. If the rectangle has an area of 108 square centimeters, what is the length of the diagonal?
18 centimeters
9 centimeters
24 centimeters
15 centimeters
12 centimeters
15 centimeters
The length and width of the rectangle are in a ratio of 3:4, so the sides can be written as 3x and 4x.
We also know the area, so we write an equation and solve for x:
(3x)(4x) = 12x2 = 108.
x2 = 9
x = 3
Now we can recalculate the length and the width:
length = 3x = 3(3) = 9 centimeters
width = 4x = 4(3) = 12 centimeters
Using the Pythagorean Theorem we can find the diagonal, c:
length2 + width2 = c2
92 + 122 = c2
81 + 144 = c2
225 = c2
c = 15 centimeters
Example Question #1 : Rectangles
The two rectangles shown below are similar. What is the length of EF?
8
6
5
10
10
When two polygons are similar, the lengths of their corresponding sides are proportional to each other. In this diagram, AC and EG are corresponding sides and AB and EF are corresponding sides.
To solve this question, you can therefore write a proportion:
AC/EG = AB/EF ≥ 3/6 = 5/EF
From this proportion, we know that side EF is equal to 10.
Example Question #1 : How To Find The Length Of The Side Of A Rectangle
A rectangle is x inches long and 3x inches wide. If the area of the rectangle is 108, what is the value of x?
3
4
6
12
8
6
Solve for x
Area of a rectangle A = lw = x(3x) = 3x2 = 108
x2 = 36
x = 6
Example Question #1 : How To Find The Length Of The Side Of A Rectangle
If the area of rectangle is 52 meters squared and the perimeter of the same rectangle is 34 meters. What is the length of the larger side of the rectangle if the sides are integers?
14 meters
15 meters
16 meters
12 meters
13 meters
13 meters
Area of a rectangle is = lw
Perimeter = 2(l+w)
We are given 34 = 2(l+w) or 17 = (l+w)
possible combinations of l + w
are 1+16, 2+15, 3+14, 4+13... ect
We are also given the area of the rectangle is 52 meters squared.
Do any of the above combinations when multiplied together= 52 meters squared? yes 4x13 = 52
Therefore the longest side of the rectangle is 13 meters
Example Question #1 : How To Find If Rectangles Are Similar
Note: Figure NOT drawn to scale.
In the above figure,
.
.
Give the perimeter of .
We can use the Pythagorean Theorem to find :
The similarity ratio of to is
so multiplied by the length of a side of is the length of the corresponding side of . We can subsequently multiply the perimeter of the former by to get that of the latter:
Example Question #3 : Rectangles
Note: Figure NOT drawn to scale.
In the above figure,
.
.
Give the area of .
Insufficient information is given to determine the area.
Corresponding sidelengths of similar polygons are in proportion, so
, so
We can use the Pythagorean Theorem to find :
The area of is
Example Question #5 : Rectangles
Note: Figure NOT drawn to scale.
In the above figure,
.
.
Give the area of Polygon .
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.