Examples with solutions for Perimeter of a Rectangle: Using variables

Exercise #1

Look at the following rectangle:

AAABBBCCCDDDX+3X+2

The perimeter of the rectangle is 26.

Calculate the value of X.

Video Solution

Step-by-Step Solution

Since in a rectangle every pair of opposite sides are equal, we can claim that:

AD=BC=x+2 AD=BC=x+2

AB=CD=x+3 AB=CD=x+3

Since the perimeter of the rectangle is equal to 26, we can substitute the data into the formula:

26=x+2+x+3+x+2+x+3 26=x+2+x+3+x+2+x+3

26=4x+10 26=4x+10

2610=4x 26-10=4x

16=4x 16=4x

Let's divide both sides by 4:

4=x 4=x

Answer

4

Exercise #2

Look at the following rectangle:

AAABBBCCCDDD4X+32X+1

The perimeter of the rectangle is 20.

Calculate the value of X.

Video Solution

Step-by-Step Solution

Since in a rectangle every pair of opposite sides are equal, we can claim that:

AD=BC=2x+1 AD=BC=2x+1

AB=CD=4x+3 AB=CD=4x+3

Since the perimeter of the rectangle is equal to 20, we can substitute the data into the formula:

20=2x+1+4x+3+2x+1+4x+3 20=2x+1+4x+3+2x+1+4x+3

20=12x+8 20=12x+8

208=12x 20-8=12x

12=12x 12=12x

Let's divide both sides by 12:

1=x 1=x

Answer

1 1

Exercise #3

Look at the following rectangle:
AAABBBCCCDDDX+1420

The area of the rectangle is 20.

What is the perimeter of rectangle ABCD?

Video Solution

Step-by-Step Solution

The area of the rectangle equals its length multiplied by its width:

S=AB×AD S=AB\times AD

Let's first substitute the data into the formula:

20=4×(x+1) 20=4\times(x+1)

20=4x+4 20=4x+4

204=4x 20-4=4x

16=4x 16=4x

4=x 4=x

Now we can calculate side AB:

4+1=5 4+1=5

The perimeter of the rectangle equals the sum of its sides.

Since each pair of opposite sides are equal in a rectangle, we can calculate that:

AD=BC=4 AD=BC=4

AB=CD=5 AB=CD=5

Finally, let's add all the sides together to find the perimeter:

4+5+4+5=8+10=18 4+5+4+5=8+10=18

Answer

18

Exercise #4

Given the following rectangle:

The perimeter of the rectangle is 32.

Find the value of the parameter x.

AAABBBCCCDDD102x

Video Solution

Step-by-Step Solution

To solve this problem, let's clearly follow these steps:

  • Step 1: Identify the information given and needed for solving.

  • Step 2: Apply the perimeter formula for a rectangle.

  • Step 3: Solve for the unknown variable x x .

Step 1: The rectangle has a perimeter P=32 P = 32 . One pair of opposite sides is 2x 2x and the other pair is 10.

Step 2: The perimeter of a rectangle is calculated by
P=2(l+w) P = 2(l + w) where l l is the length and w w is the width.
Here, l=2x l = 2x and w=10 w = 10 .

Step 3: Substitute the given values into the formula:

32=2(2x+10) 32 = 2(2x + 10)

Expand the equation:

32=4x+20 32 = 4x + 20

To solve for x x , subtract 20 from both sides:

3220=4x 32 - 20 = 4x

12=4x 12 = 4x

Finally, divide both sides by 4 to find x x :

x=124 x = \frac{12}{4}

x=3 x = 3

Therefore, the solution to the problem is x=3 x = 3 .

Answer

3

Exercise #5

The perimeter of the rectangle below is 28.

Calculate the value of x.

AAABBBCCCDDDx11

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Identify the given information
  • Step 2: Use the perimeter formula
  • Step 3: Solve for x x

Now, let's work through each step:

Step 1: The problem gives us that the perimeter of the rectangle is 28, one side (length) is 11, and the other side (width) is x x .
Step 2: We'll use the formula for the perimeter of a rectangle: P=2(l+w) P = 2(l + w) . In this problem, l=11 l = 11 and w=x w = x so:

28=2(11+x) 28 = 2(11 + x)

Step 3: Divide both sides by 2 to isolate the expression inside the parentheses:

14=11+x 14 = 11 + x

Step 4: Subtract 11 from both sides to solve for x x :

x=1411=3 x = 14 - 11 = 3

Therefore, the value of x x is 3 3 .

Answer

3

Exercise #6

The perimeter of the rectangle below is 12.

Calculate x.
AAABBBCCCDDDx2x

Video Solution

Step-by-Step Solution

To solve this problem, we will determine x x using the perimeter formula for a rectangle. The steps are as follows:

  • Step 1: Set up the perimeter equation for this problem using the formula P=2(l+w) P = 2(l + w) .
  • Step 2: Identify the given dimensions: l=2x l = 2x and w=x w = x .
  • Step 3: Substitute these dimensions into the perimeter equation: 2(2x+x)=12 2(2x + x) = 12 .
  • Step 4: Simplify the equation to solve for x x .

Now, let's follow these steps:

Step 1: The perimeter P=12 P = 12 units. Thus, we use the equation:

2(l+w)=12 2(l + w) = 12

Step 2: Substitute the known values of length and width:

2(2x+x)=12 2(2x + x) = 12

Step 3: Simplify the equation inside the parentheses:

2(3x)=12 2(3x) = 12

Step 4: Divide both sides by 2 to solve for x x :

3x=6 3x = 6

Finally, divide by 3:

x=2 x = 2

Therefore, the solution to the problem is x=2 x = 2 .

Answer

2

Exercise #7

The perimeter of the rectangle below is 8.

Calculate x.

AAABBBCCCDDD4+2xx-3

Video Solution

Step-by-Step Solution

To find x x , we'll use the concept of the rectangle's perimeter.

Step 1: Identify the given expressions for length and width.

  • Length L=4+2x L = 4 + 2x
  • Width W=x3 W = x - 3
  • Perimeter P=8 P = 8

Step 2: Use the formula for the perimeter of a rectangle: P=2(L+W) P = 2(L + W) .

Substitute the given expressions into the formula:

8=2((4+2x)+(x3)) 8 = 2((4 + 2x) + (x - 3))

Step 3: Simplify the equation within the parentheses:

8=2(4+2x+x3) 8 = 2(4 + 2x + x - 3) 8=2(1+3x) 8 = 2(1 + 3x)

Step 4: Distribute the 2:

8=2×1+2×3x 8 = 2 \times 1 + 2 \times 3x 8=2+6x 8 = 2 + 6x

Step 5: Solve for x x :

82=6x 8 - 2 = 6x 6=6x 6 = 6x x=1 x = 1

Therefore, the value of x x is 1.

Answer

1

Exercise #8

The perimeter of the rectangle below is 24.

Calculate x.

AAABBBCCCDDD4x-8x-10

Video Solution

Step-by-Step Solution

To solve this problem, we'll use the perimeter of a rectangle formula:

  • Step 1: Identify the side lengths.
  • Step 2: Use the perimeter formula to set up the equation.
  • Step 3: Solve for x x .

Now, let's work through each step:

Step 1: The side lengths are x10 x - 10 and 4x8 4x - 8 .
Step 2: The perimeter P P is given by 2(x10)+2(4x8)=24 2(x - 10) + 2(4x - 8) = 24 .

Simplify the equation:

2(x10)+2(4x8)=24 2(x - 10) + 2(4x - 8) = 24 2x20+8x16=24 2x - 20 + 8x - 16 = 24

Combine like terms:

10x36=24 10x - 36 = 24

Step 3: Solve for x x :

10x=24+36 10x = 24 + 36 10x=60 10x = 60 x=6 x = 6

Therefore, the value of x x is 6 \boxed{6} .

Answer

6

Exercise #9

Look at the following rectangle:

AAABBBCCCDDD6X+29

Given that the area of the triangle ABD is 9, what is the perimeter of the rectangle ABCD?

Video Solution

Step-by-Step Solution

Area of triangle ADB:

AD×AB2 \frac{AD\times AB}{2}

Let's list the known data:

9=x+2×62 9=\frac{x+2\times6}{2}

9=(x+2)×3 9=(x+2)\times3

9=3x+6 9=3x+6

96=3x 9-6=3x

3=3x 3=3x

1=x 1=x

Side AD equals:

1+2=3 1+2=3

Since in a rectangle, each pair of opposite sides are equal, we can state that:

AD=BC=3 AD=BC=3

AB=CD=6 AB=CD=6

Now we can calculate the perimeter of the rectangle:

3+6+3+6=6+12=18 3+6+3+6=6+12=18

Answer

18

Exercise #10

Look at the following rectangle:

AAABBBCCCDDD10X+26

Given that the perimeter of the triangle BCD is 20, what is the perimeter of the rectangle ABCD?

Video Solution

Step-by-Step Solution

Given that the perimeter of triangle BCD is 20

We can therefore insert the existing data and calculate as follows:

20=10+6+x+2 20=10+6+x+2

20=16+x+2 20=16+x+2

20162=x 20-16-2=x

x=2 x=2

Now we can calculate the BC side: 2+2=4

Perimeter of the rectangle ABCD:

6+6+4+4=12+8=20 6+6+4+4=12+8=20

Answer

20

Exercise #11

The rectangle below is composed of two smaller rectangles.

Calculate x given that the perimeter of rectangle AEFD is 30.

AAABBBCCCDDDEEEFFF4+2x2x+32-x

Video Solution

Step-by-Step Solution

To solve the problem, we'll begin by setting up the equation for the perimeter of rectangle AEFD AEFD :

The perimeter P P of a rectangle is given by the formula:

P=2×(length+width) P = 2 \times (\text{length} + \text{width})

We're told that the perimeter of rectangle AEFD AEFD is 30. The length is 2x+3 2x + 3 and the width is 2x 2 - x . Thus, the perimeter equation is:

2×((2x+3)+(2x))=30 2 \times ((2x + 3) + (2 - x)) = 30

Let's simplify the expression inside the parentheses:

=2×((2x+3)+2x) = 2 \times ((2x + 3) + 2 - x) =2×(x+5) = 2 \times (x + 5)

So the equation becomes:

2×(x+5)=30 2 \times (x + 5) = 30

Now, distribute the 2:

2x+10=30 2x + 10 = 30

Subtract 10 from both sides of the equation:

2x=20 2x = 20

Divide both sides by 2 to solve for x x :

x=10÷2 x = 10 \div 2 x=2 x = 2

Therefore, the value of x x that satisfies the given perimeter is x=2 x = 2 .

Answer

2

Exercise #12

The rectangle below is composed of two smaller rectangles.

Calculate x given that the perimeter of rectangle ABCD is 48.

AAABBBCCCDDDEEEFFF5+x3-x8+2x

Video Solution

Step-by-Step Solution

To solve the problem of finding x x given the perimeter of rectangle ABCD, we follow these steps:

  • Step 1: The problem states that the perimeter of rectangle ABCD is 48. The expressions related to x x represent sides of this rectangle.
  • Step 2: Identify the sides using expressions in the diagram:
    • The complete top and bottom sides (width) are divided into 3x 3-x and full vertical is 5+x 5+x .
    • One vertical height is 8+2x 8+2x .
  • Step 3: Use the perimeter formula for a rectangle: P=2(width+height) P = 2(\text{width} + \text{height}) .
  • Step 4: Substitute in the formula and solve for x x .

Now, let's apply these steps:

Express the perimeter using the given: 2((3x)+(5+x))+2(8+2x)=48 2((3-x) + (5+x)) + 2(8+2x) = 48 .

Simplify the equation:

2(3x+5+x)+2(8+2x)=48 2(3-x + 5+x) + 2(8+2x) = 48

2(8)+2(8+2x)=48 2(8) + 2(8+2x) = 48

16+16+4x=48 16 + 16 + 4x = 48

Combine like terms:

32+4x=48 32 + 4x = 48

Isolate 4x 4x :

4x=4832 4x = 48 - 32

4x=16 4x = 16

Solve for x x :

x=164 x = \frac{16}{4}

x=4 x = 4

Therefore, the value of x x is x=4 x = 4 .

Answer

4

Exercise #13

The rectangle in the diagram is composed of of three smaller rectangles.

Calculate x given that GDEF has a perimeter of 44.

AAABBBCCCGGGFFFDDDEEE10x-83+x5x

Video Solution

Step-by-Step Solution

Let's calculate the perimeter of rectangle GDEF using the given data:

10x8+10x8+5x+5x=44 10x-8+10x-8+5x+5x=44

We'll group similar terms:

30x16=44 30x-16=44

30x=44+16 30x=44+16

30x=60 30x=60

x=2 x=2

Answer

2

Exercise #14

Look at the following rectangle:

AAABBBCCCDDDX+5X-17

The area of the rectangle is 7.

What is the perimeter of the rectangle?

Video Solution

Step-by-Step Solution

To solve this problem, we'll need to find the value of X X and then use this value to find the perimeter of the rectangle. Follow these detailed steps:

  • Step 1: Set up the equation for the area.
    Given the area of the rectangle is 7, and the sides are (X+5) (X + 5) and (X1) (X - 1) , the equation becomes:

(X+5)(X1)=7(X + 5)(X - 1) = 7
Expanding the left side, we have: X2+5XX5=7 X^2 + 5X - X - 5 = 7 X2+4X5=7 X^2 + 4X - 5 = 7

  • Step 2: Simplify and solve the quadratic equation.
    By moving all terms to one side, we have:

X2+4X57=0 X^2 + 4X - 5 - 7 = 0 X2+4X12=0 X^2 + 4X - 12 = 0

  • Step 3: Factor the quadratic equation.
    We factor the equation as:

(X+6)(X2)=0 (X + 6)(X - 2) = 0

  • Step 4: Solve for X X using the zero-product property.
    The solutions for X X are:

X+6=0X=6 X + 6 = 0 \Rightarrow X = -6 X2=0X=2 X - 2 = 0 \Rightarrow X = 2

  • Step 5: Use the positive X X value to find the perimeter.
    Since dimensions cannot be negative, X=2 X = 2 . Thus, the rectangle’s dimensions become:

Length=X+5=2+5=7 \text{Length} = X + 5 = 2 + 5 = 7
Width=X1=21=1 \text{Width} = X - 1 = 2 - 1 = 1

  • Step 6: Calculate the perimeter using the dimensions.

P=2×(Length+Width)=2×(7+1)=2×8=16 P = 2 \times (\text{Length} + \text{Width}) = 2 \times (7 + 1) = 2 \times 8 = 16

Therefore, the perimeter of the rectangle is 16.

Answer

16

Exercise #15

The shape below is composed of three rectangles.

Calculate x given that the perimeter of rectangle GCHF is 18.

AAABBBCCCGGGFFFHHHDDDEEE10x-83+x5x

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Write the expression for the perimeter of rectangle GCHF using the given variables.
  • Step 2: Set up the equation by equating the expression to 18.
  • Step 3: Solve the equation for x x .

Let's work through each step:

Step 1: The perimeter of rectangle GCHF is given by the formula:

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

According to the diagram, the dimensions of the rectangle GCHF are:

- GH = 3+x 3 + x (length),

- GF = 5x 5x (width).

Thus, the perimeter formula becomes:

2×(3+x)+2×(5x) 2 \times (3 + x) + 2 \times (5x)

Step 2: Set the equation equal to the given perimeter, 18:

2(3+x)+2(5x)=18 2(3 + x) + 2(5x) = 18

Step 3: Simplify and solve for x x :

Distribute the 2:

6+2x+10x=18 6 + 2x + 10x = 18

Combine like terms:

6+12x=18 6 + 12x = 18

Subtract 6 from both sides:

12x=12 12x = 12

Divide both sides by 12 to isolate x x :

x=1 x = 1

Therefore, the solution to the problem is x=1 x = 1 .

Answer

1

Exercise #16

The area of the square whose side length is 4 cm is
equal to the area of the rectangle whose length of one of its sides is 1 cm.

What is the perimeter of the rectangle?

Video Solution

Step-by-Step Solution

After squaring all sides, we can calculate the area as follows:

42=16 4^2=16

Since we are given that the area of the square equals the area of the rectangle , we will write an equation with an unknown since we are only given one side length of the parallelogram:

16=1×x 16=1\times x

x=16 x=16

In other words, we now know that the length and width of the rectangle are 16 and 1, and we can calculate the perimeter of the rectangle as follows:

1+16+1+16=32+2=34 1+16+1+16=32+2=34

Answer

34

Exercise #17

The perimeter of the rectangle below is 36.

Calculate the value of x.

AAABBBCCCDDD4x

Video Solution

Answer

4

Exercise #18

The rectangle below is composed of two rectangles.

Calculate the value of the x, given that the perimeter of the rectangle is 48.

AAABBBCCCDDD7xx

Video Solution

Answer

2

Exercise #19

The rectangle below is composed of two smaller rectangles.

Calculate x given that the perimeter of rectangle ABCD is 42.

AAABBBCCCDDDEEEFFF4+2x2x+32-x

Video Solution

Answer

4

Exercise #20

The shape below is composed of three rectangles.

Calculate X given that the perimeter of rectangle CDEH is 90.

AAABBBCCCGGGFFFHHHDDDEEE10x-83+x5x

Video Solution

Answer

4