Basic Geometry : How to find the area of a rectangle

Study concepts, example questions & explanations for Basic Geometry

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Example Questions

Example Question #51 : How To Find The Area Of A Rectangle

If the perimeter of a rectangle is \displaystyle 24, and the width of the rectangle is \displaystyle 10, what is the area of the rectangle?

Possible Answers:

\displaystyle 26

\displaystyle 22

\displaystyle 20

\displaystyle 24

Correct answer:

\displaystyle 20

Explanation:

Recall how to find the perimeter of a rectangle:

\displaystyle \text{Perimeter}=2(\text{length}+\text{width})

Since we are given the width and the perimeter, we can solve for the length.

\displaystyle \text{length}+\text{width}=\frac{\text{Perimeter}}{2}

\displaystyle \text{length}=\frac{\text{Perimeter}}{2}-\text{width}

Substitute in the given values for the width and perimeter to find the length.

\displaystyle \text{length}=\frac{24}{2}-10

Simplify.

\displaystyle \text{length}=12-10

Solve.

\displaystyle \text{length}=2

Now, recall how to find the area of a rectangle.

\displaystyle \text{Area}=\text{length}\times\text{width}

Substitute in the values of the length and width to find the area.

\displaystyle \text{Area}=10 \times 2

Solve.

\displaystyle \text{Area}=20

Example Question #602 : Plane Geometry

If the perimeter of a rectangle is \displaystyle 24, and the width of the rectangle is \displaystyle 9, what is the area of the rectangle?

Possible Answers:

\displaystyle 18

\displaystyle 36

\displaystyle 9

\displaystyle 27

Correct answer:

\displaystyle 27

Explanation:

Recall how to find the perimeter of a rectangle:

\displaystyle \text{Perimeter}=2(\text{length}+\text{width})

Since we are given the width and the perimeter, we can solve for the length.

\displaystyle \text{length}+\text{width}=\frac{\text{Perimeter}}{2}

\displaystyle \text{length}=\frac{\text{Perimeter}}{2}-\text{width}

Substitute in the given values for the width and perimeter to find the length.

\displaystyle \text{length}=\frac{24}{2}-9

Simplify.

\displaystyle \text{length}=12-9

Solve.

\displaystyle \text{length}=3

Now, recall how to find the area of a rectangle.

\displaystyle \text{Area}=\text{length}\times\text{width}

Substitute in the values of the length and width to find the area.

\displaystyle \text{Area}=3 \times 9

Solve.

\displaystyle \text{Area}=27

Example Question #53 : How To Find The Area Of A Rectangle

If the perimeter of a rectangle is \displaystyle 24, and the width of the rectangle is \displaystyle 8, what is the area of the rectangle?

Possible Answers:

\displaystyle 32

\displaystyle 36

\displaystyle 44

\displaystyle 40

Correct answer:

\displaystyle 32

Explanation:

Recall how to find the perimeter of a rectangle:

\displaystyle \text{Perimeter}=2(\text{length}+\text{width})

Since we are given the width and the perimeter, we can solve for the length.

\displaystyle \text{length}+\text{width}=\frac{\text{Perimeter}}{2}

\displaystyle \text{length}=\frac{\text{Perimeter}}{2}-\text{width}

Substitute in the given values for the width and perimeter to find the length.

\displaystyle \text{length}=\frac{24}{2}-8

Simplify.

\displaystyle \text{length}=12-8

Solve.

\displaystyle \text{length}=4

Now, recall how to find the area of a rectangle.

\displaystyle \text{Area}=\text{length}\times\text{width}

Substitute in the values of the length and width to find the area.

\displaystyle \text{Area}=8 \times 4

Solve.

\displaystyle \text{Area}=32

Example Question #601 : Basic Geometry

If the perimeter of a rectangle is \displaystyle 24, and the width of the rectangle is \displaystyle 7, what is the area of the rectangle?

Possible Answers:

\displaystyle 40

\displaystyle 35

\displaystyle 30

\displaystyle 25

Correct answer:

\displaystyle 35

Explanation:

Recall how to find the perimeter of a rectangle:

\displaystyle \text{Perimeter}=2(\text{length}+\text{width})

Since we are given the width and the perimeter, we can solve for the length.

\displaystyle \text{length}+\text{width}=\frac{\text{Perimeter}}{2}

\displaystyle \text{length}=\frac{\text{Perimeter}}{2}-\text{width}

Substitute in the given values for the width and perimeter to find the length.

\displaystyle \text{length}=\frac{24}{2}-7

Simplify.

\displaystyle \text{length}=12-7

Solve.

\displaystyle \text{length}=5

Now, recall how to find the area of a rectangle.

\displaystyle \text{Area}=\text{length}\times\text{width}

Substitute in the values of the length and width to find the area.

\displaystyle \text{Area}=7 \times 5

Solve.

\displaystyle \text{Area}=35

Example Question #51 : How To Find The Area Of A Rectangle

A rectangle has a width of \displaystyle 5in, and a lenth of \displaystyle 12in. Find the perimeter. 

Possible Answers:

\displaystyle 39in

\displaystyle 60in

\displaystyle 30in

\displaystyle 25in

\displaystyle 34in

Correct answer:

\displaystyle 34in

Explanation:

To find perimeter, you add the sides of the rectangle together. In this case, that would be:

\displaystyle Perimeter = 12 + 12 + 5 + 5

\displaystyle P = 34

Example Question #51 : How To Find The Area Of A Rectangle

Find the area of a rectangle given length 7 and width 8.

Possible Answers:

\displaystyle 15

\displaystyle 28

\displaystyle 56

\displaystyle 30

Correct answer:

\displaystyle 56

Explanation:

To solve, simply use the formulaf or the area of a rectangle. Thus,

\displaystyle A=l*w=7*8=56

Example Question #202 : Rectangles

Find the area of a rectangle given length of 5 and width of 7.

Possible Answers:

\displaystyle 35

\displaystyle 24

\displaystyle 12

\displaystyle \frac{35}{2}

Correct answer:

\displaystyle 35

Explanation:

To find the area of a rectangle multiply the width and base together.

To solve, simply use the formula for the area of a rectangle.

Let,

\displaystyle \\w=7 \\l=5.

Thus,

\displaystyle A=l*w=5*7=35.

Example Question #52 : How To Find The Area Of A Rectangle

Find the area of a rectanlge with width 4 and length 7.

Possible Answers:

\displaystyle 14

\displaystyle 11

\displaystyle 28

\displaystyle 22

Correct answer:

\displaystyle 28

Explanation:

To solve, simply use the formula for the area of a rectangle.

\displaystyle A=w*l=4*7=28

Example Question #53 : How To Find The Area Of A Rectangle

Find the area of a square with side length 2.

Possible Answers:

\displaystyle 4

\displaystyle 16

\displaystyle 2

\displaystyle 8

Correct answer:

\displaystyle 4

Explanation:

To solve, simply use the formula for the area of a square. Thus,

\displaystyle A=s^2=2^2=4

Example Question #55 : How To Find The Area Of A Rectangle

 

If a rectangle has a width of \displaystyle 2.3\;cm and a length that is double the width, what would be the area of the rectangle? Round to the nearest tenth.

Possible Answers:

\displaystyle 10.6\;cm^2

\displaystyle 6.9\;cm^2

\displaystyle 9.2\;cm^2

\displaystyle 5.3\;cm^2

\displaystyle 13.8\;cm^2

Correct answer:

\displaystyle 10.6\;cm^2

Explanation:

To calculate the area of a triangle, we want to multiply the length by the width. Since the length is twice that of the width, which is \displaystyle 2.3\;cm, we can determine length as such:

\displaystyle 2.3\;cm\cdot2=4.6\;cm

Now that we know the values for length and width, we can calculate the area of the triangle:

\displaystyle Area=2.3\;cm\cdot4.6\;cm=10.6\;cm^2

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