When students hear the words "compound shapes", they usually feel uncomfortable. Just before you also ask yourself: "Oh, why this again?", you should be aware that there is no real reason. Describing shapes as compound doesn't really make them so. As it turns out calculating areas and perimeters of compound shapes is in fact relatively straightforward.
You will be introduced to Complex shapes only after you learn various shapes in geometry. The reason these shapes are complex is due to the fact that they are slightly different from those you've come to know. In each complex shape, additional shapes that you need to identify are hidden. Dividing the complex shape into several different (and familiar) shapes will allow you to answer the question of how to calculate the area of complex shapes.
The trick: extract a familiar shape from within the complex shape
So how do we answer the question of how to calculate the area of complex shapes? First, you need to identify familiar shapes within the complex shape. An example of this: a rectangle. As you know, each shape has properties that you are familiar with, so within the complex shape itself, you can apply the properties of the familiar shape and thus calculate areas and perimeters.
After completing the missing data (according to the properties of each shape, for example: rectangle), you can complete the "puzzle", identify additional data that is revealed to you, and thus calculate the area of the complex shape. When calculating the area of complex shapes, you will often need to perform simple arithmetic operations such as division and addition (mainly for sides in the shape) - all based on the unique properties of each shape.
When students hear the words "compound shapes", they usually feel uncomfortable. Just before you also ask yourself: "Oh, why this again?", you should know that there really is no reason. Describing shapes as compound doesn't really make them so. As it turns out calculating areas and perimeters of compound shapes can actually be relatively straightforward.
You will be introduced to Complex shapes only after you learn various shapes in geometry. The reason these shapes are complex is due to the fact that they are slightly different from those you've come to know. In each complex shape, additional shapes that you need to identify are hidden. Dividing the complex shape into several different (and familiar) shapes will allow you to answer the question of how to calculate the area of complex shapes.
The trick: extract a familiar shape from within the complex shape
So how do we answer the question of how to calculate the area of complex shapes? First, you need to identify familiar shapes within the complex shape. For example: a rectangle. As you know, each shape has properties that you are familiar with, so within the complex shape itself, you can apply the properties of the familiar shape and thus calculate areas and perimeters.
After completing the missing data (according to the properties of each shape, for example: rectangle), you can complete the "puzzle", identify additional data that becomes apparent, and thus calculate the area of the compound shape. When calculating the area of compound shapes, you will often need to perform simple arithmetic operations like division and addition (especially for sides in the shape) - all based on the unique properties of each shape.
For example: Assuming the composite shape includes several different rectangles, based on the given side lengths, it will be possible to calculate the different areas. The area of a rectangle is calculated using the formula length X width. When the side lengths are visible, subtraction and addition can be performed (according to the sizes of the rectangles and their positions within the shape) of sides, and thus calculate the area of the shape, as seen in the example below.
To calculate the shape's area - we will divide it in a way that creates two rectangles. We will find the area by adding and/or subtracting rectangles.
In this division we created:
A rectangle with size 9⋅2=18 rectangle A
A rectangle with size 8⋅6=48 rectangle B
The area of the entire composite shape is:
9⋅2+8⋅6=66
or
48+18=66
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Test your knowledge
Question 1
What is the area of the triangle in the drawing?
Incorrect
Correct Answer:
17.5
Question 2
Calculate the area of the parallelogram based on the data in the figure:
Incorrect
Correct Answer:
It is not possible to calculate.
Question 3
A parallelogram has a length equal to 6 cm and a height equal to 4.5 cm.
Calculate the area of the parallelogram.
Incorrect
Correct Answer:
27
Examples with solutions for Area of a Rectangle
Exercise #1
What is the area of the given triangle?
Video Solution
Step-by-Step Solution
This question is a bit confusing. We need start by identifying which parts of the data are relevant to us.
Remember the formula for the area of a triangle:
The height is a straight line that comes out of an angle and forms a right angle with the opposite side.
In the drawing we have a height of 6.
It goes down to the opposite side whose length is 5.
And therefore, these are the data points that we will use.
We replace in the formula:
26×5=230=15
Answer
15
Exercise #2
What is the area of the triangle in the drawing?
Video Solution
Step-by-Step Solution
First, we will identify the data points we need to be able to find the area of the triangle.
the formula for the area of the triangle: height*opposite side / 2
Since it is a right triangle, we know that the straight sides are actually also the heights between each other, that is, the side that measures 5 and the side that measures 7.
We multiply the legs and divide by 2
25×7=235=17.5
Answer
17.5
Exercise #3
Calculate the area of the parallelogram based on the data in the figure:
Video Solution
Step-by-Step Solution
In this particular problem, despite being given certain measurements, the diagram lacks sufficient clarity to identify which corresponds definitively as the base and which as the perpendicular height of the parallelogram. This insufficiency means that without further context or labeling to avoid assumptions that may lead to error, it is not feasible to calculate the area confidently using the standard formula.
Thus, the answer to the problem is that it is not possible to calculate the area with the provided data.
Answer
It is not possible to calculate.
Exercise #4
A parallelogram has a length equal to 6 cm and a height equal to 4.5 cm.
Calculate the area of the parallelogram.
Video Solution
Step-by-Step Solution
To solve this problem, let's apply the formula for the area of a parallelogram:
The formula for the area of a parallelogram is Area=base×height.
Here, the base of the parallelogram is 6 cm, and the height is 4.5 cm.
Substituting these values into the formula gives:
Area=6×4.5
Performing the multiplication:
Area=27 square centimeters.
Therefore, the area of the parallelogram is 27cm2.
Referring to the given multiple-choice answers, the correct choice is:
Choice 3: 27.
Answer
27
Exercise #5
Calculate the area of the parallelogram using the data in the figure:
Video Solution
Step-by-Step Solution
To solve this problem, we'll follow these steps:
Step 1: Identify the given information
Step 2: Apply the appropriate formula
Step 3: Perform the necessary calculations
Now, let's work through each step:
Step 1: The problem provides us with a base (b) of 7 units and a height (h) of 5 units, perpendicular to this base.
Step 2: We'll apply the formula for the area of a parallelogram, which is Area=b×h.
Step 3: Substituting the given values, Area=7×5=35.
Therefore, the area of the parallelogram is 35 square units.