Examples with solutions for Area of a Rectangle: Using additional geometric shapes

Exercise #1

A deltoid-shaped stage is to be built in a rectangular field.

The length of the field is 30 m and the width is 20 m.

What is the area of the stage shaded in orange?

202020303030AAABBBCCCDDD

Video Solution

Step-by-Step Solution

We can calculate the area of rectangle ABCD like so:

20×30=600 20\times30=600

Now let's divide the deltoid along its length and width and add the following points:

202020303030PPPMMMNNNKKKAAABBBCCCDDDFinally, we can calculate the area of deltoid PMNK as follows:

PMNK=PN×MK2=20×302=6002=300 PMNK=\frac{PN\times MK}{2}=\frac{20\times30}{2}=\frac{600}{2}=300

Answer

300 m

Exercise #2

Given: the length of a rectangle is 3 greater than its width.

The area of the rectangle is equal to 27 cm².

Calculate the length of the rectangle

2727273x3x3xxxx

Video Solution

Step-by-Step Solution

The area of the rectangle is equal to length multiplied by width.

Let's set up the data in the formula:

27=3x×x 27=3x\times x

27=3x2 27=3x^2

273=3x23 \frac{27}{3}=\frac{3x^2}{3}

9=x2 9=x^2

x=9=3 x=\sqrt{9}=3

Answer

x=3 x=3

Exercise #3

The trapezoid ABCD and the rectangle ABGE are shown in the figure below.

Given in cm:

AB = 5

BC = 5

GC = 3

Calculate the area of the rectangle ABGE.

555555333AAABBBCCCDDDEEEGGG

Video Solution

Step-by-Step Solution

Let's calculate side BG using the Pythagorean theorem:

BG2+GC2=BC2 BG^2+GC^2=BC^2

We'll substitute the known data:

BG2+32=52 BG^2+3^2=5^2

BG2+9=25 BG^2+9=25

BG2=16 BG^2=16

BG=16=4 BG=\sqrt{16}=4

Now we can calculate the area of rectangle ABGE since we have the length and width:

5×4=20 5\times4=20

Answer

20

Exercise #4

ABCD is a parallelogram and AEFD is a rectangle.

AE = 7

The area of AEFD is 35 cm².

CF = 2

What is the area of the parallelogram?

S=35S=35S=35777222AAAEEEDDDFFFCCCBBB

Video Solution

Step-by-Step Solution

Let's first calculate the sides of the rectangle:

AEDF=AE×ED AEDF=AE\times ED

Let's input the known data:

35=7×ED 35=7\times ED

Let's divide the two legs by 7:

ED=5 ED=5

Since AEDF is a rectangle, we can claim that:

ED=FD=7

Let's calculate side CD:

2+7=9 2+7=9

Let's calculate the area of parallelogram ABCD:

ABCD=CD×ED ABCD=CD\times ED

Let's input the known data:

ABCD=9×5=45 ABCD=9\times5=45

Answer

45 cm².

Exercise #5

Given that: the area of the rectangle is equal to 36.

AE=14AB AE=\frac{1}{4}AB

363636333AAABBBDDDCCCEEE

Find the size of AE.

Video Solution

Step-by-Step Solution

The area of rectangle ABCD equals length multiplied by width.

Let's input the known data into the formula in order to find side AB:

36=3×AB 36=3\times AB

Let's divide both sides by 3:

AB=12 AB=12

Since we are given that AE equals a quarter of AB, we can substitute the known data and calculate side AE:

AE=14AB=14×12=3 AE=\frac{1}{4}AB=\frac{1}{4}\times12=3

Answer

3

Exercise #6

Shown below is the rectangle ABCD.

Given in cm:

AK = 5

DK = 4

The area of the rectangle is 24 cm².

Calculate the side AB.

S=24S=24S=24555444AAABBBCCCDDDKKK

Video Solution

Step-by-Step Solution

Let's look at triangle ADK to calculate side AD:

AD2+DK2=AK2 AD^2+DK^2=AK^2

Let's input the given data:

AD2+42=52 AD^2+4^2=5^2

AD2+16=25 AD^2+16=25

We'll move 16 to the other side and change the appropriate sign:

AD2=2516 AD^2=25-16

AD2=9 AD^2=9

We'll take the square root and get:

AD=3 AD=3

Since AD is a side of rectangle ABCD, we can calculate side AB as follows:

S=AB×AD S=AB\times AD

Let's input the given data:

24=3×AB 24=3\times AB

We'll divide both sides by 3:

AB=8 AB=8

Answer

8

Exercise #7

The area of the rectangle below is equal to 45.

ED=13AB ED=\frac{1}{3}AB

454545555AAABBBDDDCCCEEE

Calculate the size of ED.

Video Solution

Step-by-Step Solution

The area of rectangle ABCD equals length times width.

Let's write down the known data in a formula to find side CD:

45=5×CD 45=5\times CD

Let's divide both sides by 5:

CD=9 CD=9

We know that in a rectangle, each pair of opposite sides are equal, therefore:

AB=CD=9 AB=CD=9

Since we are given that ED equals one-third of CD, we can substitute the known data and calculate side ED:

Remember that AB equals CD

ED=13AB=13×9=3 ED=\frac{1}{3}AB=\frac{1}{3}\times9=3

Answer

3

Exercise #8

The area of the rectangle is equal to 70.

EB=15AB EB=\frac{1}{5}AB

AAABBBDDDCCCEEE707

Calculate the length of EB.

Video Solution

Step-by-Step Solution

The area of rectangle ABCD equals length multiplied by width.

Let's use the known data in the formula to find side AB:

70=7×AB 70=7\times AB

Let's divide both sides by 7:

AB=10 AB=10

Since we are given that EB equals one-fifth of AB, we can use the known data and calculate side EB:

EB=15AB=15×10=2 EB=\frac{1}{5}AB=\frac{1}{5}\times10=2

Answer

2

Exercise #9

Given the rectangle ABCD

Given BC=X and the side AB is larger by 4 cm than the side BC.

The area of the triangle ABC is 8X cm².

What is the area of the rectangle?

S=8XS=8XS=8XX+4X+4X+4XXXAAABBBCCCDDD

Video Solution

Step-by-Step Solution

Let's calculate the area of triangle ABC:

8x=(x+4)x2 8x=\frac{(x+4)x}{2}

Multiply by 2:

16x=(x+4)x 16x=(x+4)x

Divide by x:

16=x+4 16=x+4

Let's move 4 to the left side and change the sign accordingly:

164=x 16-4=x

12=x 12=x

Now let's calculate the area of the rectangle, multiply the length and width where BC equals 12 and AB equals 16:

16×12=192 16\times12=192

Answer

192

Exercise #10

The area of the rectangle in the drawing is 28X cm².

What is the area of the circle?

S=28XS=28XS=28X777

Video Solution

Step-by-Step Solution

Let's draw the center of the circle and we can divide the diameter of the circle into two equal radii

Now let's calculate the length of the radii as follows:

7×2r=28x 7\times2r=28x

14r=28x 14r=28x

We'll divide both sides by 14:

r=2814x r=\frac{28}{14}x

r=2x r=2x

Let's calculate the circumference of the circle:

P=2π×r=2π×2x=4πx P=2\pi\times r=2\pi\times2x=4\pi x

Answer

4πx 4\pi x

Exercise #11

The height of the house in the drawing is 12x+9 12x+9

its width x+2y x+2y

Given the ceiling height is half the height of the square section.

Express the area of the house shape in the drawing band x and and.

Video Solution

Step-by-Step Solution

Let's draw a line in the middle of the drawing that divides the house into 2

Meaning it divides the triangle and the rectangular part.

The 2 lines represent the heights in both shapes.

If we connect the height of the roof with the height of the rectangular part, we get the total height

Let's put the known data in the formula:

12hsquare+hsquare=12x+9 \frac{1}{2}h_{\text{square}}+h_{square}=12x+9

32hsquare=12x+9 \frac{3}{2}h_{\text{square}}=12x+9

We'll multiply by two thirds and get:

hsquare=2(12x+9)3=2(4x+3) h_{\text{square}}=\frac{2(12x+9)}{3}=2(4x+3)

hsquare=8x+6 h_{\text{square}}=8x+6

If the height of the triangle equals half the height of the rectangular part, we can calculate it using the following formula:

htriangle=12(8x+6)=4x+3 h_{\text{triangle}}=\frac{1}{2}(8x+6)=4x+3

Now we can calculate the area of the triangular part:

(x+2y)×(4x+3)2=4x2+3x+8xy+6y2=2x2+1.5x+4xy+3y \frac{(x+2y)\times(4x+3)}{2}=\frac{4x^2+3x+8xy+6y}{2}=2x^2+1.5x+4xy+3y

Now we can calculate the rectangular part:

(x+2y)×(8x+6)=8x2+6x+16xy+12y (x+2y)\times(8x+6)=8x^2+6x+16xy+12y

Now let's combine the triangular area with the rectangular area to express the total area of the shape:

S=2x2+1.5x+4xy+3y+8x2+6x+16xy+12y S=2x^2+1.5x+4xy+3y+8x^2+6x+16xy+12y

S=10x2+20xy+7.5x+15y S=10x^2+20xy+7.5x+15y

Answer

3x2+8xy+112x+4y2+3y 3x^2+8xy+1\frac{1}{2}x+4y^2+3y

Exercise #12

Below is a hexagon that contains a rectangle inside it.

The area of the rectangle is 28 cm².

777

What is the area of the hexagon?

Video Solution

Step-by-Step Solution

Since we are given the area of the rectangle, let's first work out the length of the missing side:

7×a=28 7\times a=28

We'll now divide both sides by 7 to get:

a=4 a=4

Since all sides are equal in a hexagon, each side is equal to 4.

Now let's calculate the area of the hexagon:

6×a2×34 \frac{6\times a^2\times\sqrt{3}}{4}

6×42×34 \frac{6\times4^2\times\sqrt{3}}{4}

Finally, we simplify the exponent in the denominator of the fraction to get:

6×4×3=24×3=41.56 6\times4\times\sqrt{3}=24\times\sqrt{3}=41.56

Answer

41.56