SSAT Upper Level Math : Areas and Perimeters of Polygons

Study concepts, example questions & explanations for SSAT Upper Level Math

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Example Questions

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

The perimeter of a square is equal to the circumference of a circle with area 4. What is the area of the square?

Possible Answers:

Correct answer:

Explanation:

First, we need the radius  of the circle, which can be determined from the area of a circle formula by setting :

Simplifying the expression by splitting the radicand and rationalizing the denominator:

The circumference of the circle is  multiplied by the radius, or

This is also the perimeter of the square, so the length of each side is one fourth of this perimeter, or

The area of the square is the square of this common sidelength, or 

.

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

A square and a circle have the same area. The circle has diameter 10. Which expression is equal to the length of one side of the square?

Possible Answers:

Correct answer:

Explanation:

A circle with diameter 10 has radius half this, or 5. The area of the circle can be found using the formula

,

setting :

.

The square also has this area. The length of one side of this square is equal to the square root of this, which is

Simplify this by breaking the radicand, as follows:

Example Question #61 : Areas And Perimeters Of Polygons

Right triangle 6

A square has the same area as the above right triangle. Give the length of one side of the square.

Possible Answers:

Correct answer:

Explanation:

The area of a right triangle is equal to half the product of the lengths of its legs. Since we know the lengths of one leg and the hypotenuse, we can calculate the length of the other leg using the Pythagorean Theorem. We can use this form:

Setting  and  equal to the lengths of the hypotenuse and the known leg - 13 and 5, respectively:

The area of the above triangle is

The square also has this area. The length of one side of this square is equal to the square root of this, which is .

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

The length and width of a rectangle are  and . Give its perimeter in terms of .

Possible Answers:

Correct answer:

Explanation:

A rectangle has perimeter  the length and  the width. Substitute  and  in the perimeter formula, and simplify.

Example Question #61 : Areas And Perimeters Of Polygons

A rectangle has length 30 inches and width 25 inches. Which of the following is true about its perimeter?

Possible Answers:

Its perimeter is between 8 and 9 feet.

Its perimeter is between 4 and 5 feet.

Its perimeter is between 9 and 10 feet.

Its perimeter is between 10 and 11 feet.

Its perimeter is between 5 and 6 feet.

Correct answer:

Its perimeter is between 9 and 10 feet.

Explanation:

In inches, the perimeter of the rectangle can be calculated by substituting  in the following formula:

The perimeter is 110 inches.

Now divide by 12 to convert to feet:

This makes the perimeter 9 feet 2 inches, which is between 9 feet and 10 feet.

Example Question #2 : How To Find The Perimeter Of A Rectangle

Perimeter of a rectangle is 36 inches. If the width of the rectangle is 3 inches less than its length, give the length and width of the rectangle.

Possible Answers:

 inches

inches

 inches

 inches

 inches

Correct answer:

inches

Explanation:

Let:

The perimeter of a rectangle is , where  is the length and  is the width of the rectangle. The perimeter is known so we can set up an equation in terms of and solve it:

 

So we can get:

inches

inches

 

 

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

The length and width of a rectangle are  and , respectively. Give its perimeter in terms of .

Possible Answers:

Correct answer:

Explanation:

The perimeter of a rectangle is , where  is the length and  is the width of the rectangle. In order to find the perimeter we can substitute the  and  in the perimeter formula:

Example Question #2 : How To Find The Perimeter Of A Rectangle

The length of a rectangle is and the width of this rectangle is  meters shorter than its length. Give its perimeter in terms of .

Possible Answers:

Correct answer:

Explanation:

The length of the rectangle is known, so we can find the width in terms of :

 

 

 

The perimeter of a rectangle is , where  is the length and  is the width of the rectangle.

 

In order to find the perimeter we can substitute the  and  in the perimeter formula:

 

Example Question #5 : How To Find The Perimeter Of A Rectangle

A rectangle has a length of inches and a width of inches. Which of the following is true about the rectangle perimeter if ?

Possible Answers:

Its perimeter is less than 7 feet.

Its perimeter is between 7.2 and 7.4 feet.

Its perimeter is between 7 and 8 feet.

Its perimeter is between 8 and 9 feet.

Its perimeter is more than 8 feet.

Correct answer:

Its perimeter is between 7 and 8 feet.

Explanation:

Substitute to get and :

 

 

The perimeter of a rectangle is  , where is the length and  is the width of the rectangle. So we have:

 

inches

 

Now we should divide the perimeter by 12 in order to convert to feet:

 

 feet

 

So the perimeter is 7 feet and 6 inches, which is between 7 and 8 feet.

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

Which of these polygons has the same perimeter as a rectangle with length 55 inches and width 15 inches?

Possible Answers:

A regular octagon with sidelength two feet

A regular hexagon with sidelength two feet

A regular heptagon with sidelength two feet

The other answer choices are incorrect.

A regular pentagon with sidelength two feet

Correct answer:

The other answer choices are incorrect.

Explanation:

The perimeter of a rectangle is twice the sum of its length and its width; a rectangle with dimensions 55 inches and 15 inches has perimeter 

 inches.

All of the polygons in the choices are regular - that is, all have congruent sides - and all have sidelength two feet, or 24 inches, so we divide 140 by 24 to determine how many sides such a polygon would need to have a perimeter equal to the rectangle. However, 

,

so there cannot be a regular polygon with these characteristics. All of the choices fail, so the correct response is that none are correct.

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