ISEE Upper Level Quantitative : Plane Geometry

Study concepts, example questions & explanations for ISEE Upper Level Quantitative

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Example Questions

Example Question #9 : How To Find The Area Of A Rectangle

Rectangle

Give the area of the above rectangle in terms of 

Possible Answers:

Correct answer:

Explanation:

The area of a rectangle is equal to the product of its length and height, which here are 5 and . This product is .

Example Question #10 : How To Find The Area Of A Rectangle

A rectangle is two feet shorter than twice its width; its perimeter is six yards. Give its area in square inches.

Possible Answers:

Correct answer:

Explanation:

The length of the rectangle is two feet, or 24 inches, shorter than twice the width, so, if  is the width in inches,  the length in inches is 

Six yards, the perimeter of the rectangle, is equal to  inches. The perimeter, in terms of length and width, is , so we can set up the equation:

The length and width are 64 inches and 44 inches; the area is their product, which is 

 square inches

Example Question #281 : Geometry

The perimeter of a rectangle is 210 inches. The width of the rectangle is 40% of its length. What is the area of the rectangle?

Possible Answers:

Correct answer:

Explanation:

If the width of the rectangle is 40% of the length, then 

.

The perimeter of the rectangle is:

 

The perimeter is 210 inches, so we can solve for the length:

 

The length and width of the rectangle are 75 and 30 inches; the area is their product, or

 square inches.

Example Question #282 : Geometry

 is a positive integer. 

Rectangle A has length  and width ; Rectangle B has length  and length . Which is the greater quantity?

(A) The area of Rectangle A

(B) The area of Rectangle B

Possible Answers:

(A) and (B) are equal

It is impossible to determine which is greater from the information given

(A) is greater

(B) is greater

Correct answer:

(A) is greater

Explanation:

This might be easier to solve if you set .

Then the dimensions of Rectangle A are  and . The area of Rectangle A is their product:

 

The dimensions of Rectangle B are  and .  The area of Rectangle B is their product:

 

 regardless of the value of  (or, subsequently, ), so Rectangle A has the greater area.

Example Question #11 : How To Find The Area Of A Rectangle

In Rectangle  and . Give the area of this rectangle in terms of .

Possible Answers:

Correct answer:

Explanation:

The area of a rectangle is the product of its length and its width, which here are  and . Mulitply:

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

Which is the greater quantity?

(a) The length of a diagonal of a square with sidelength 20 inches

(b) The length of a diagonal of a rectangle with length 25 inches and width less than 10 inches

Possible Answers:

(a) and (b) are equal

(b) is greater 

(a) is greater 

It is impossible to tell which is greater from the information given

Correct answer:

(a) is greater 

Explanation:

The lengths of the diagonals of these rectangles can be computed using the Pythagorean Theorem:

(a) 

(b) 

 so . Since the diagonal of the rectangle in (b) measures less than , it must also measure less than that of the square in (a)

Example Question #11 : Rectangles

In Rectangle  , , the diagonals intersect at a point .

Which is the greater quantity?

(a) 

(b) 

Possible Answers:

(a) and (b) are equal.

(b) is greater.

(a) is greater.

It is impossible to tell from the information given.

Correct answer:

(a) and (b) are equal.

Explanation:

The diagonals of a rectangle are congruent and bisect each other. Therefore,  is equidistant from all four vertices, making . The relationship between the sides is not relevant here.

Example Question #3 : How To Find The Length Of The Diagonal Of A Rectangle

Rectangle  has length 60 inches and width 80 inches. The two diagonals of the rectangle intersect at point . Which is the greater quantity?

(a) 

(b)

Possible Answers:

It is impossible to tell from the information given.

(a) is greater.

(a) and (b) are equal.

(b) is greater.

Correct answer:

(a) is greater.

Explanation:

Two consecutive sides of a rectangle and a diagonal form a right triangle, so the length of any diagonal can be determined using the Pythagorean Theorem, substituting :

The diagonals of a rectangle bisect each other. Therefore, the distance from a vertex to the point of intersection is half this, and .

Example Question #4 : How To Find The Length Of The Diagonal Of A Rectangle

A rectangle has perimeter 140 inches and area 1,200 square inches. Which is the greater quantity?

(A) The length of a diagonal of the rectangle.

(B) 4 feet

Possible Answers:

It is impossible to determine which is greater from the information given

(A) is greater

(A) and (B) are equal

(B) is greater

Correct answer:

(A) is greater

Explanation:

Let and  be the dimensions of the rectangle. Then 

 and, subsequently, 

Since the product of the length and width is the area, we are looking for two numbers whose sum is 70 and whose product is 1,200; through trial and error, they are found to be 30 and 40. We can assign either to be  and the other to be  since the result is the same.

The length of a diagonal of the rectangle  can be found by applying the Pythagorean Theorem:

A diagonal is 50 inches long; since 4 feet are equivalent to 48 inches, (A) is the greater quantity.

Example Question #81 : Quadrilaterals

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:

5x + 5

10(x + 1)

5x + 10

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)

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