Area of an isosceles trapezoid

How to calculate the area of an isosceles trapezoid?

In order to calculate the area of an isosceles trapezoid, like every trapezoid's area, we need to multiply the height by the sum of the bases and divide by 22.
That is:

Diagram of a isosceles-angled trapezoid with the formula for calculating its area:  ( Base 1 + Base 2 ) × height (Base 1+Base 2)×height. The illustration highlights the two parallel bases, the height, and the application of the formula to find the area. Featured in a tutorial on calculating the area of trapezoids.


Important point – The midsegment of a trapezoid equals half the sum of the bases

Practice Area of a Trapezoid

Examples with solutions for Area of a Trapezoid

Exercise #1

Given the trapezoid:

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What is the area?

Video Solution

Step-by-Step Solution

Formula for the area of a trapezoid:

(base+base)2×altura \frac{(base+base)}{2}\times altura

We substitute the data into the formula and solve:

9+122×5=212×5=1052=52.5 \frac{9+12}{2}\times5=\frac{21}{2}\times5=\frac{105}{2}=52.5

Answer

52.5

Exercise #2

The trapezoid ABCD is shown below.

Base AB = 6 cm

Base DC = 10 cm

Height (h) = 5 cm

Calculate the area of the trapezoid.

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Video Solution

Step-by-Step Solution

First, we need to remind ourselves of how to work out the area of a trapezoid:

Formula for calculating trapezoid area

Now let's substitute the given data into the formula:

(10+6)*5 =
2

Let's start with the upper part of the equation:

16*5 = 80

80/2 = 40

Answer

40 cm²

Exercise #3

The trapezoid ABCD is shown below.

AB = 2.5 cm

DC = 4 cm

Height (h) = 6 cm

Calculate the area of the trapezoid.

2.52.52.5444h=6h=6h=6AAABBBCCCDDD

Video Solution

Step-by-Step Solution

First, let's remind ourselves of the formula for the area of a trapezoid:

A=(Base + Base) h2 A=\frac{\left(Base\text{ }+\text{ Base}\right)\text{ h}}{2}

We substitute the given values into the formula:

(2.5+4)*6 =
6.5*6=
39/2 = 
19.5

Answer

1912 19\frac{1}{2}

Exercise #4

The trapezoid ABCD is shown below.

AB = 5 cm

DC = 9 cm

Height (h) = 7 cm

Calculate the area of the trapezoid.

555999h=7h=7h=7AAABBBCCCDDD

Video Solution

Step-by-Step Solution

The formula for the area of a trapezoid is:

Area=12×(Base1+Base2)×Height \text{Area} = \frac{1}{2} \times (\text{Base}_1 + \text{Base}_2) \times \text{Height}

We are given the following dimensions:

  • Base AB=5AB = 5 cm
  • Base DC=9DC = 9 cm
  • Height h=7h = 7 cm

Substituting these values into the formula, we have:

Area=12×(5+9)×7 \text{Area} = \frac{1}{2} \times (5 + 9) \times 7

First, add the lengths of the bases:

5+9=14 5 + 9 = 14

Now substitute back into the formula:

Area=12×14×7 \text{Area} = \frac{1}{2} \times 14 \times 7

Calculate the multiplication:

12×14=7 \frac{1}{2} \times 14 = 7

Then multiply by the height:

7×7=49 7 \times 7 = 49

Thus, the area of the trapezoid is 49 cm2^2.

Answer

49 cm

Exercise #5

What is the area of the trapezoid in the diagram below?

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Video Solution

Step-by-Step Solution

To determine the area of the trapezoid, we will follow these steps:

  • Step 1: Identify the provided dimensions of the trapezoid.
  • Step 2: Apply the formula for the area of a trapezoid.
  • Step 3: Perform the arithmetic to calculate the area.

Let's proceed through these steps:

Step 1: Identify the dimensions
The given dimensions from the diagram are:
Height h=3 h = 3 cm.
One base b1=4 b_1 = 4 cm.
The other base b2=7 b_2 = 7 cm.

Step 2: Apply the area formula
To find the area A A of the trapezoid, use the formula:
A=12×(b1+b2)×h A = \frac{1}{2} \times (b_1 + b_2) \times h

Step 3: Calculation
Substituting the known values into the formula:
A=12×(4+7)×3 A = \frac{1}{2} \times (4 + 7) \times 3

Simplify the expression:
A=12×11×3 A = \frac{1}{2} \times 11 \times 3

Calculate the result:
A=12×33=332=16.5 A = \frac{1}{2} \times 33 = \frac{33}{2} = 16.5 cm²

The area of the trapezoid is therefore 16.5 16.5 cm².

Given the choices, this corresponds to choice : 16.5 16.5 cm².

Therefore, the correct solution to the problem is 16.5 16.5 cm².

Answer

16.5 16.5 cm²

Exercise #6

What is the area of the trapezoid in the diagram?

555138

Video Solution

Step-by-Step Solution

To find the area of the trapezoid, we will follow these steps:

  • Step 1: Identify the given dimensions of the trapezoid.
  • Step 2: Apply the area formula for a trapezoid using these dimensions.
  • Step 3: Perform the calculation to determine the area.

Let's work through each step more clearly:
Step 1: From the problem, we identify that the trapezoid has one base b1=13b_1 = 13 units, another base b2=8b_2 = 8 units, and its height h=5h = 5 units.
Step 2: The formula for the area of a trapezoid is:

A=12×(b1+b2)×h A = \frac{1}{2} \times (b_1 + b_2) \times h

Step 3: Substitute the values into the formula:

A=12×(13+8)×5 A = \frac{1}{2} \times (13 + 8) \times 5

A=12×21×5 A = \frac{1}{2} \times 21 \times 5

A=12×105 A = \frac{1}{2} \times 105

A=52.5units2 A = 52.5 \, \text{units}^2

Therefore, the area of the trapezoid is 52.5units2 52.5 \, \text{units}^2 .

Answer

52.5 52.5 cm²

Exercise #7

What is the area of the trapezoid in the figure?

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Video Solution

Step-by-Step Solution

We use the following formula to calculate the area of a trapezoid: (base+base) multiplied by the height divided by 2:

(AB+DC)×BE2 \frac{(AB+DC)\times BE}{2}

(7+15)×22=22×22=442=22 \frac{(7+15)\times2}{2}=\frac{22\times2}{2}=\frac{44}{2}=22

Answer

22 22 cm².

Exercise #8

What is the area of the trapezoid in the figure?

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Video Solution

Step-by-Step Solution

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

  • Step 1: Identify the given information relevant to the trapezoid.
  • Step 2: Apply the appropriate formula for the area of a trapezoid.
  • Step 3: Perform the necessary calculations to find the area.

Now, let's work through each step:
Step 1: The problem gives us two bases, b1=6 b_1 = 6 cm and b2=12 b_2 = 12 cm, and a height h=4 h = 4 cm.
Step 2: We'll use the formula for the area of a trapezoid: A=12(b1+b2)h A = \frac{1}{2} \cdot (b_1 + b_2) \cdot h
Step 3: Substituting in the given values: A=12(6+12)4=12184=722=36 cm2 A = \frac{1}{2} \cdot (6 + 12) \cdot 4 = \frac{1}{2} \cdot 18 \cdot 4 = \frac{72}{2} = 36 \text{ cm}^2

Therefore, the solution to the problem is 36 36 cm².

Answer

36 36 cm².

Exercise #9

What is the area of the trapezoid in the figure?

6.56.56.5101010444AAABBBCCCDDDEEE

Video Solution

Step-by-Step Solution

To solve this problem, we'll compute the area of the trapezoid using the given dimensions and the area formula:

  • Step 1: Identify the given dimensions:
    • Base b1=10 b_1 = 10 cm
    • Base b2=6.5 b_2 = 6.5 cm
    • Height h=4 h = 4 cm
  • Step 2: Use the trapezoid area formula:
  • The formula for the area of a trapezoid is A=12(b1+b2)h A = \frac{1}{2}(b_1 + b_2)h .

  • Step 3: Substitute the given values into the formula:
  • A=12(10+6.5)×4 A = \frac{1}{2}(10 + 6.5) \times 4

  • Step 4: Calculate the area:
  • First, calculate the sum of the bases: 10+6.5=16.5 10 + 6.5 = 16.5 .

    Next, multiply by the height: 16.5×4=66 16.5 \times 4 = 66 .

    Finally, divide by 2 to get the area: 662=33\frac{66}{2} = 33 cm².

Therefore, the area of the trapezoid is 33 33 cm².

Answer

33 33 cm².

Exercise #10

Given the following trapezoid:

AAABBBCCCDDD584

Calculate the area of the trapezoid ABCD.

Video Solution

Step-by-Step Solution

To solve this problem, we follow these steps:

  • Step 1: Identify the given dimensions of the trapezoid.
  • Step 2: Use the formula for the area of a trapezoid.
  • Step 3: Substitute the given values into the formula and calculate the area.

Now, let's work through these steps:

Step 1: We know from the problem that trapezoid ABCD has bases AB=5 AB = 5 and CD=8 CD = 8 , with a height of AD=4 AD = 4 .

Step 2: The formula for the area of a trapezoid is:
A=12×(b1+b2)×h A = \frac{1}{2} \times (b_1 + b_2) \times h

Step 3: Plugging in the values:
A=12×(5+8)×4=12×13×4=522=26 A = \frac{1}{2} \times (5 + 8) \times 4 = \frac{1}{2} \times 13 \times 4 = \frac{52}{2} = 26

Therefore, the area of the trapezoid ABCD is 26 26 .

Answer

26

Exercise #11

Given the following trapezoid:

AAABBBCCCDDD795

Calculate the area of the trapezoid ABCD.

Video Solution

Step-by-Step Solution

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

  • Step 1: Identify the lengths of the trapezoid's bases: AB=7 AB = 7 and CD=9 CD = 9 .
  • Step 2: Identify the height of the trapezoid: AD=5 AD = 5 .
  • Step 3: Apply the trapezoid area formula: A=12×(b1+b2)×h A = \frac{1}{2} \times (b_1 + b_2) \times h .
  • Step 4: Calculate the area using the values from Steps 1 and 2.

Now, let us work through each step:
Step 1: The length of base AB AB is (b1=7)(b_1 = 7) units, and the length of base CD CD is (b2=9)(b_2 = 9) units.
Step 2: The height AD AD is (h=5)(h = 5) units.

Step 3: Substitute the known values into the formula for the area of a trapezoid:
A=12×(7+9)×5 A = \frac{1}{2} \times (7 + 9) \times 5

Step 4: Calculate the results:
A=12×16×5=12×80=40 A = \frac{1}{2} \times 16 \times 5 = \frac{1}{2} \times 80 = 40

Therefore, the area of trapezoid ABCD is 40\mathbf{40} square units.

Answer

40

Exercise #12

Given the following trapezoid:

AAABBBCCCDDD683

Calculate the area of the trapezoid ABCD.

Video Solution

Step-by-Step Solution

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

  • Step 1: Recall the formula for the area of a trapezoid.
  • Step 2: Substitute the given values into the formula.
  • Step 3: Calculate the area using arithmetic operations.

Let's work through each step:
Step 1: The formula for the area of a trapezoid is given by:
Area=12×(Base1+Base2)×Height \text{Area} = \frac{1}{2} \times (\text{Base}_1 + \text{Base}_2) \times \text{Height}
Step 2: Plug in the values: Base1=AB=6\text{Base}_1 = AB = 6, Base2=CD=8\text{Base}_2 = CD = 8, and the height AD=3AD = 3.
Area=12×(6+8)×3 \text{Area} = \frac{1}{2} \times (6 + 8) \times 3
Step 3: Perform the calculations:
Area=12×14×3=12×42=21 \text{Area} = \frac{1}{2} \times 14 \times 3 = \frac{1}{2} \times 42 = 21

Therefore, the area of trapezoid ABCDABCD is 2121.

Answer

21

Exercise #13

Given the following trapezoid:

AAABBBCCCDDD5104

Calculate the area of the trapezoid ABCD.

Video Solution

Step-by-Step Solution

To solve this problem, we'll calculate the area of trapezoid ABCD using the appropriate formula.

The formula for the area A A of a trapezoid is given by:

A=12×(Base1+Base2)×Height A = \frac{1}{2} \times (\text{Base}_1 + \text{Base}_2) \times \text{Height}

Substituting the given values into the formula, we have:

A=12×(5+10)×4 A = \frac{1}{2} \times (5 + 10) \times 4

First, calculate the sum of the bases:

5+10=15 5 + 10 = 15

Multiply by the height, and then take half:

A=12×15×4=12×60=30 A = \frac{1}{2} \times 15 \times 4 = \frac{1}{2} \times 60 = 30

Therefore, the area of the trapezoid ABCD is 30 square units.

Answer

30

Exercise #14

Given the following trapezoid:

AAABBBCCCDDD7115

Calculate the area of the trapezoid ABCD.

Video Solution

Step-by-Step Solution

To calculate the area of the trapezoid ABCD, we will follow these steps:

Given:

  • Base AB=7 AB = 7
  • Base CD=11 CD = 11
  • Height =5 = 5

Apply the trapezoid area formula:

The formula for the area of a trapezoid is:

A=12×(Base1+Base2)×Height A = \frac{1}{2} \times (\text{Base}_1 + \text{Base}_2) \times \text{Height}

Substitute the values into the formula:

A=12×(7+11)×5 A = \frac{1}{2} \times (7 + 11) \times 5

Simplify the expression:

A=12×18×5 A = \frac{1}{2} \times 18 \times 5

Calculate:

A=12×90 A = \frac{1}{2} \times 90

Finally, compute the area:

A=45 A = 45

Thus, the area of trapezoid ABCD is 45 45 .

Answer

45

Exercise #15

What is the area of the trapezoid ABCD?

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Video Solution

Step-by-Step Solution

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

  • Identify the given measurements: the lengths of the parallel sides (bases) and the height.
  • Use the trapezoid area formula to calculate the area.
  • Perform the necessary arithmetic to find the numerical answer.

Now, let's work through each step:
Step 1: The given measurements are Base1=9 \text{Base}_1 = 9 , Base2=12 \text{Base}_2 = 12 , and the height = 5.
Step 2: The formula for the area of a trapezoid is Area=12×(Base1+Base2)×Height \text{Area} = \frac{1}{2} \times (\text{Base}_1 + \text{Base}_2) \times \text{Height} .
Step 3: Substituting the numbers into the formula, we have:
Area=12×(9+12)×5 \text{Area} = \frac{1}{2} \times (9 + 12) \times 5

Calculating inside the parentheses first:
9+12=21 9 + 12 = 21

Then multiply by the height:
21×5=105 21 \times 5 = 105

Finally, multiply by one-half:
12×105=52.5 \frac{1}{2} \times 105 = 52.5

Therefore, the area of trapezoid ABCD ABCD is 52.5 52.5 .

Answer

52.5