Area of a Rectangle
Lesson Objective
In this lesson, we will learn about the area of a rectangle.
About This Lesson
In this lesson, we will:
- Learn about the formula to find the area of a rectangle.
- See an example on using the formula to calculate a rectangle's area.
- See another example on using the formula to calculate the width of a rectangle.
The study tips and math video below will explain more.
Study Tips
Tip #1
A rectangle has four right angles. The sides of a rectangle that are opposite each other have the same length.
Note that, the longer side of a rectangle is the length and the shorter side is the width. Also, a square is a special type of rectangle.
Now, for a rectangle with length l and width w, its area, A will be:
The math video below will give more explanation on this. Also, we will see some examples on how to use this formula.
Math Video
Math Video Transcript
00:00:03.150
In this lesson, we will learn about the area of a rectangle.
00:00:08.22
Consider this rectangle with the length of L, and the width of W.
00:00:14.080
Now, we can get the area of the rectangle, by multiplying its length L with its width W.
00:00:21.150
With this, we get the area, A equals to, L multiply W. This gives LW.
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Note that, it is very important to include the unit. Since we are multiplying L with W, the unit for the area will be in the form of square unit.
00:00:41.240
We will see more explanations on this in the upcoming example.
00:00:46.170
Now, let's see some examples on using this formula.
00:00:51.090
Find the area of this rectangle when its length is 4cm, and its width is 3cm.
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To solve this, we start with the formula for the area of a rectangle, A equals to LW.
00:01:06.150
Since the length is given as 4cm, we can substitute L with 4.
00:01:13.020
Similarly, since the width is given as 3cm, we can substitute w with 3.
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Next, we can simplify by multiplying 4 with 3. This gives 12.
00:01:27.220
Now, this number is meaningless unless we include the unit for it.
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Since the length and width are given in centimeter, the unit for the area will be in square centimeter.
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Hence, the area of this rectangle is 12 square centimeter.
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Next example, given that the area of this rectangle is 20 square feet, and its length is 5ft. Find its width.
00:01:56.100
Again, we start with the formula for the area of a rectangle, A equals to LW.
00:02:03.060
Since the value of the area and the length is given, we can find the width, by solving this equation for w.
00:02:10.110
Here’s how. Since the area is given as 20 square feet, we can substitute A with 20.
00:02:17.140
Similarly, since the length is given as 5ft, we can substitute l with 5.
00:02:24.060
Now we have, 5w equals to 20.
00:02:28.160
Let's rewrite this equation so that it will look neater.
00:02:32.230
To find W, we need to remove 5. To do so, we divide both sides of the equation with 5.
00:02:42.060
After doing so, we have, W equals to 20 over 5.
00:02:48.080
20 divide by 5 gives 4.
00:02:51.180
Now, this number is meaningless unless we include the unit for it.
00:02:56.160
Since the length is given in feet, the width of the rectangle will also be in feet.
00:03:02.040
Therefore, the width of this rectangle is 4 ft.
00:03:07.110
That is all for this lesson. Try out the practice question to further your understanding.
Practice Questions & More
Multiple Choice Questions (MCQ)
Now, let's try some MCQ questions to understand this lesson better.
You can start by going through the series of questions on the area of a rectangle or pick your choice of question below.
- Question 1 on finding the area of a rectangle
- Question 2 on finding the width of a rectangle
Site-Search and Q&A Library
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