Area of Isosceles Trapezoid Practice Problems with Solutions

Master calculating area of isosceles trapezoids with step-by-step practice problems. Learn formulas, properties, and midsegment concepts through guided examples.

📚Practice Calculating Isosceles Trapezoid Areas
  • Apply the trapezoid area formula: (base₁ + base₂) × height ÷ 2
  • Identify equal legs, base angles, and diagonals in isosceles trapezoids
  • Use midsegment properties to find missing base measurements
  • Calculate height when given area and base measurements
  • Solve multi-step problems involving perpendicular heights
  • Work with coordinate geometry and trapezoid vertices

Understanding Area of a Trapezoid

Complete explanation with examples

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

Detailed explanation

Practice Area of a Trapezoid

Test your knowledge with 21 quizzes

Calculate the area of the trapezoid.

555141414666

Examples with solutions for Area of a Trapezoid

Step-by-step solutions included
Exercise #1

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

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}

Video Solution
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.

666101010h=5h=5h=5AAABBBCCCDDD

Step-by-Step Solution

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

(Base+Base)h2=Area \frac{(Base+Base)\cdot h}{2}=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

Video Solution
Exercise #3

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

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

Video Solution
Exercise #4

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

777333AAABBBCCCDDDEEEFFF4

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

Video Solution
Exercise #5

What is the area of the trapezoid in the diagram?

555138

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

Video Solution

Frequently Asked Questions

What is the formula for area of an isosceles trapezoid?

+
The area formula is: Area = (base₁ + base₂) × height ÷ 2. This is the same formula used for all trapezoids, including isosceles trapezoids.

How do you find the height of an isosceles trapezoid?

+
The height is the perpendicular distance between the parallel bases. You can identify it by looking for a 90° angle marker or by using given measurements and the Pythagorean theorem.

What makes an isosceles trapezoid different from a regular trapezoid?

+
An isosceles trapezoid has three special properties: 1) Equal legs (non-parallel sides), 2) Equal base angles, and 3) Equal diagonals. These properties create symmetry that regular trapezoids don't have.

How does the midsegment help calculate trapezoid area?

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The midsegment equals half the sum of the bases. If you know the midsegment length, multiply by 2 to get the sum of bases, then use the area formula: midsegment × 2 × height ÷ 2.

What information do I need to find a trapezoid's area?

+
You need: 1) The lengths of both parallel bases, 2) The height (perpendicular distance between bases). Alternatively, you can use the midsegment length instead of individual base lengths.

Can I use the same area formula for all types of trapezoids?

+
Yes, the formula Area = (base₁ + base₂) × height ÷ 2 works for all trapezoids: isosceles, right-angled, and scalene trapezoids.

How do I solve trapezoid area problems with missing measurements?

+
Use the given information systematically: 1) Identify what you know and what you need, 2) Apply trapezoid properties (like equal legs in isosceles), 3) Use geometry relationships to find missing values, 4) Substitute into the area formula.

What are common mistakes when calculating trapezoid area?

+
Common errors include: forgetting to divide by 2, confusing legs with bases, using the wrong height measurement, and not recognizing when a segment is the midsegment rather than a base.

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