Geometric shapes, like the trapezoid, are all around us. Learning to work with these shapes will open doors for us in our studies as well as helping us to understand the world around us.
Let's start with finding the area of a trapezoid, one of the most important fundamental exercises.
Let's start at the beginning - What is a trapezoid?
A trapezoid is a quadrilateral that has one pair of parallel sides, which are called bases.
There are several types of trapezoids, like the isosceles trapezoid (whose non-parallel sides have the same length, and their diagonals are equal), and the rectangular trapezoid (which has one side perpendicular to its bases).
Some quadrilaterals are often confused with the trapezoid, such as the parallelogram. However, the parallelogram has two pairs of parallel sides while the trapezoid has only one pair of parallelsides.
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Test your knowledge
Question 1
Calculate the area of the trapezoid.
Incorrect
Correct Answer:
It cannot be calculated.
Question 2
Calculate the area of the trapezoid.
Incorrect
Correct Answer:
19 1/2
Question 3
What is the area of the trapezoid ABCD?
Incorrect
Correct Answer:
52.5
Finding the area of a trapezoid
The formula to use to calculate the area of a trapezoid is as follows:
Base 1 (b1) plus base 2 (b2) times height (h) times two.isosceles, we know that
AFS=2(B1+B2)×h
Now that you have reviewed the formula for finding the area of a trapezoid, here are three exercises to practice:
Example problems
Example 1 - area of an isosceles trapezoid
Suppose we have an isosceles trapezoid (whose non-parallel sides are equal) with the following values:
The length of the upper base that starts at the vertex A and ends at the vertex B is 6cm.
The length of the lower base starting at the vertex D and ending at the vertex C is 8cm.
The height, which is represented by the letter h (from the word 'height'), is 4cm.
The sum of the two bases is equal to 6+8.
Then, we multiply the sum by the height (4×14), which is gives us 56.
This is then divided by 2, which is equal to 28.
Therefore, the area of this trapezoid is equal to 28 square centimeters.
28=2(6+8)×4
Do you know what the answer is?
Question 1
The trapezoid ABCD is shown below.
The height of ABCD is 6 cm.
The base BC is equal to 4 cm.
The base AD is equal to 8 cm.
Calculate the area of trapezoid ABCD.
Incorrect
Correct Answer:
36
Question 2
Given the trapezoid:
What is the area?
Incorrect
Correct Answer:
52.5
Question 3
What is the area of the trapezoid in the diagram below?
Incorrect
Correct Answer:
\( 16.5 \) cm²
Example 2 - area of a trapezoid
Suppose we have a trapezoid that is not isosceles (its non-parallel sides are not equal), and that has the following values:
The length of the base starting at vertex A and ending at vertex B is 6cm.
The length of the base starting at vertex D and ending at vertex C is 10cm.
The height (represented by the letter h) is 4cm.
The sum of the bases is
16(6+10).
Then we multiply this sum by the height(16×4), which equals 64.
Finally, we divide 64 by 2. We will get 32.
Therefore, the area of the trapezoid is32cm2 square centimeters.
32=2(6+10)×4
Example 3 - area of a rectangular trapezoid
Suppose we have a rectangular trapezoid (which has one side perpendicular to its bases) with the following values:
The length of the base starting at the vertex A and ending at the vertex B is 6cm.
The length of the base that starts at vertex D and ends at vertex C is 9cm.
The height between the bases (represented by the letter h) is 4cm.
First, we add the bases (6+9), which gives us 15. Then, we multiply 15 by the height (4×15), which equals 60. Finally, we divide 60 by 2, which equals 30. Therefore, the area of this trapezoid is equal to30cm square centimeters. Given that the trapezoid is
30=2(6+9)×4
Although it's important to study with enthusiasm and motivation in order to be prepared for your exams, it is just as important to learn how to take breaks. Whenever possible, take one day off a week from studying. Giving yourself a moment to enjoy a well-deserved rest will renew your energy and motivation and make your studying more enjoyable and stress-free.
If you are preparing for an upcoming exam, try organizing your study time with specific goals and time slots. This way, you will be able to track your progress as well as balance your study time efficiently. Lastly, remember that when preparing for exams, not all students study in the same way. Every student needs to find the method of studying that is best suited for him or her.
Check your understanding
Question 1
What is the area of the trapezoid in the diagram?
Incorrect
Correct Answer:
\( 52.5 \) cm²
Question 2
What is the area of the trapezoid in the figure?
Incorrect
Correct Answer:
\( 22 \) cm².
Question 3
What is the area of the trapezoid in the figure?
Incorrect
Correct Answer:
\( 36 \) cm².
Additional exercises
Exercise 1
How do we calculate the area of a trapezoid?
Below we are given a trapezoid with the following values:
What is its height?
Solution
Formula for the area of a trapezoid:
2(Base+Base)×height
We don't have all our values for the formula, so we will have to work backwards to find the missing height.
29+6×h=30
Now to reduce and solve:
215×h=30
721×h=30
h=21530
h=1560
h=4
Answer HeightBE is equal to4cm.
Exercise 2
Given a rectangle ABCD formed by a trapezoid AKDC and a right triangle KBC with the following measures:
DC=14cm
AD=5cm
KB=4cm
How many times is the area of the trapezoidAKCD greater than the area of the triangle KBC?
DC=14cm
AD=5cm
KB=4cm
To find out how many times the area of the trapezoid is greater than the area of the triangle, we will calculate the area of both figures and then divide the area of the trapezoid by the area of the triangle.
To find the solution, we will need to calculate the area of the triangle and the area of the trapezoid.
The formula for the area of the triangle is as follows:
2(Height×Base)
We know that the length of the base KB is 4.
The height is CB.
Since the opposite sides of the rectangle are equal we know that AD=CB.
Therefore CB=5.
Now we can calculate
4×5=20
Finally we divide by two to get the area of the triangle.
220=10
Now we will calculate the area of the trapezoid:
Aˊrea=2(AK+DC)×AD
We know the side DC=AB because opposite sides in a rectangle are equal,
And the length of KB=4,
Therefore we can calculate the length of AK.
AB−KB=AK
14−4=10
Now we can substitute the values into the formula for the area of the trapezoid.
2(14+10)×5
2(24)×5
2120=60
Now, all we have left to do is to divide the area of the trapezoid by the area of the triangle:
1060=6
Therefore, the trapezoid is six times greater than the triangle.
Answer:
The correct answer 6 times greater.
Do you think you will be able to solve it?
Question 1
What is the area of the trapezoid in the figure?
Incorrect
Correct Answer:
\( 33 \) cm².
Question 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.
Incorrect
Correct Answer:
40 cm²
Question 3
The trapezoid ABCD is shown below.
AB = 2.5 cm
DC = 4 cm
Height (h) = 6 cm
Calculate the area of the trapezoid.
Incorrect
Correct Answer:
\( 19\frac{1}{2} \)
Exercise 3
Given an isosceles trapezoid ABCD
BC=7cm
The height of the trapezoid is h=5cm
The perimeter of the trapezoid P=34cm
Calculate the area of the trapezoid
Solution:
To calculate the area of the trapezoid, we must analyze the given information.
Given that the trapezoid is isosceles, we know that BC=AD=7cm.
The given height is h=5cm.
The perimeter of the trapezoid is P=34cm.
To find the sum of the two bases AB+CD we subtract the known sides BC=AD=7 from the perimeter P
P−BC−AD=AB+DC
34−7−7=AB+DC=20cm
Now we will use that value to find the area of the trapezoid
Aˊrea=25(20)=50
Answer:
50cm2
Exercise 4
Given:
Trapezoid DECB is part of triangle △ABC which has the following values:
AB=6cm
AC=10cm
Also, we know that DE intersects AB and AC respectively.
Task:
Calculate the area of trapezoid DECB
Solution:
To find the area of the trapezoid we must first find the values of the sides BC and DE.
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Do you know what the answer is?
Question 1
Calculate the area of the trapezoid.
Incorrect
Correct Answer:
It cannot be calculated.
Question 2
Calculate the area of the trapezoid.
Incorrect
Correct Answer:
19 1/2
Question 3
What is the area of the trapezoid ABCD?
Incorrect
Correct Answer:
52.5
How many exercises do I need to solve before finding the area of trapezoids becomes easy?
The formula for finding the area of a trapezoid doesn't have to be complicated. All you need to do is review until you can remember the formula, and then you will be able to input the given values from the exercises with ease.
Also, remember that it is important to follow the order of operations in their proper order: PEMDAS (Parentheses, Exponents, Multiplication, Division, Addition and then Subtraction).
Sometimes, you may have to solve for areas of trapezoids with missing values.
However, if you are familiar with the properties of the different types of trapezoids (like isosceles and rectangular trapezoids), you will be able to find the missing values and solve for the area.
How many exercises should I practice?
Since every student learns at a different pace, the answer to this question will be individual for everyone. The important thing is to understand your current level, and know when you need to practice more and when you're ready to move on. Typically, we recommend starting by solving ten basic and medium level exercises in order to memorize the basic formula.
How can I prepare for pop quizzes?
The answer is quite simple. Many students are deathly afraid of pop quizzes, but in reality, they are an opportunity to practice and show your knowledge. The key to doing well is to study consistenly throughout the year, not just before the exams.
Knowing that there will be a test will usually motivate you to stay up to date on your homework.
Avoid falling behind on your studies, and stay on top of the latest lectures.
Exams questions usually start by testing your knowledge on one topic at a time. For example: calculate the area of a trapezoid.
Grades are based on a yearly average, so it is in your best interest to get the best possible score on each test.
As long as you pay attention in class and do your homework, you won't have to be afraid of exams.
Check your understanding
Question 1
The trapezoid ABCD is shown below.
The height of ABCD is 6 cm.
The base BC is equal to 4 cm.
The base AD is equal to 8 cm.
Calculate the area of trapezoid ABCD.
Incorrect
Correct Answer:
36
Question 2
Given the trapezoid:
What is the area?
Incorrect
Correct Answer:
52.5
Question 3
What is the area of the trapezoid in the diagram below?
Incorrect
Correct Answer:
\( 16.5 \) cm²
How do I know if I am falling behind?
Are there topics that you don't understand or can't remember learning? Some topics might seem easy to you, while some may seem more difficult - that's completely normal!
Important: don't over-procrastinate learning the course material. The pace in math courses can be fast and you don't want to get left behind. Many new topics are built on what topics you've already learned. Therefore, if you haven't taken the time to make sure you know an old topic well, you might find it hard to understand the new topic. How do you know if you are falling behind?
You find it difficult to stay concentrated in class because you don't understand the teacher.
You have difficulty doing your homework.
You have started getting lower scores on your exams.
What can I do to catch up?
You can ask a classmate to help explain what you don't understand.
Speak up and ask your math teacher to help you.
You can find a private tutor to help you strengthen the ares that you are struggling with.
Do you think you will be able to solve it?
Question 1
What is the area of the trapezoid in the diagram?
Incorrect
Correct Answer:
\( 52.5 \) cm²
Question 2
What is the area of the trapezoid in the figure?
Incorrect
Correct Answer:
\( 22 \) cm².
Question 3
What is the area of the trapezoid in the figure?
Incorrect
Correct Answer:
\( 36 \) cm².
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Test your knowledge
Question 1
What is the area of the trapezoid in the figure?
Incorrect
Correct Answer:
\( 33 \) cm².
Question 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.
Incorrect
Correct Answer:
40 cm²
Question 3
The trapezoid ABCD is shown below.
AB = 2.5 cm
DC = 4 cm
Height (h) = 6 cm
Calculate the area of the trapezoid.
Incorrect
Correct Answer:
\( 19\frac{1}{2} \)
Examples with solutions for Area of a Trapezoid
Exercise #1
Calculate the area of the trapezoid.
Video Solution
Step-by-Step Solution
We use the formula (base+base) multiplied by the height and divided by 2.
Note that we are only provided with one base and it is not possible to determine the size of the other base.
Therefore, the area cannot be calculated.
Answer
Cannot be calculated.
Exercise #2
Given the trapezoid:
What is the area?
Video Solution
Step-by-Step Solution
Formula for the area of a trapezoid:
2(base+base)×altura
We substitute the data into the formula and solve:
29+12×5=221×5=2105=52.5
Answer
52.5
Exercise #3
What is the area of the trapezoid in the figure?
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:
2(AB+DC)×BE
2(7+15)×2=222×2=244=22
Answer
22 cm².
Exercise #4
The trapezoid ABCD is shown below.
Base AB = 6 cm
Base DC = 10 cm
Height (h) = 5 cm
Calculate the area of the trapezoid.
Video Solution
Step-by-Step Solution
First, we need to remind ourselves of how to work out the area of a trapezoid:
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 #5
The trapezoid ABCD is shown below.
AB = 2.5 cm
DC = 4 cm
Height (h) = 6 cm
Calculate the area of the trapezoid.
Video Solution
Step-by-Step Solution
First, let's remind ourselves of the formula for the area of a trapezoid: