How do we calculate the area of complex shapes?

🏆Practice area of a rectangle

How do we calculate the area of complex shapes?

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.

Two composite shapes labeled with side lengths. • Left shape: A 'house-like' figure formed by a rectangle (4 units wide and 4 units high) with a triangle on top (two equal sides of 6 units, base 4 units). • Right shape: An L-shaped polygon composed of rec

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Test yourself on area of a rectangle!

Calculate the area of the parallelogram according to the data in the diagram.

101010777AAABBBCCCDDDEEE

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How do we calculate the area of complex shapes?

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.

Diagram of a composite shape divided into two labeled areas: 'A' and 'B.' Dimensions provided for the sides: 2, 3, 6, 8, 9, and 10 units.

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 92=189 \cdot2 = 18 rectangle AA

A rectangle with size ​​​​86=48​​​​8 \cdot 6 = 48 rectangle BB

The area of the entire composite shape is:

92+86=669\cdot2+8\cdot6=66

or

48+18=6648 + 18= 66

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Examples with solutions for Area of a Rectangle

Exercise #1

Given the deltoid ABCD

Find the area

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Video Solution

Step-by-Step Solution

To solve this problem, we need to calculate the area of the deltoid ABCDABCD using the given lengths of its diagonals. The formula for the area of a deltoid (kite) is:

A=12×d1×d2 A = \frac{1}{2} \times d_1 \times d_2

Where d1d_1 and d2d_2 are the lengths of the diagonals. From the diagram, we know:

  • Diagonal AC=7AC = 7 cm
  • Diagonal BD=5BD = 5 cm

Substituting these values into the formula, we have:

A=12×7×5 A = \frac{1}{2} \times 7 \times 5

Calculating this gives:

A=12×35=17.5 A = \frac{1}{2} \times 35 = 17.5

Therefore, the area of the deltoid ABCDABCD is 17.517.5 cm².

The correct answer from the given choices is:

17.5 17.5 cm².

Answer

17.5 17.5 cm².

Exercise #2

Given the deltoid ABCD

Find the area

999666AAADDDCCCBBB

Video Solution

Step-by-Step Solution

To solve the problem of finding the area of the deltoid (kite) ABCD, we will apply the formula for the area of a kite involving its diagonals:

The formula is:
Area=12×d1×d2\text{Area} = \frac{1}{2} \times d_1 \times d_2

Where d1d_1 and d2d_2 are the lengths of the diagonals. From the problem’s illustration:

  • Diagonal d1d_1 (AC): Not visible in numbers, assumed to be covered internally or derived from setup, but logically follows as one given median-symmetry related.
  • Diagonal d2d_2 (BD): The vertical line gives a length of 6 cm6\text{ cm} from point B to D on the vertical axis.

The image references imply through markings that their impact in shape is demonstrated via convergence of matching altitudes and isos of plot. The diagonal proportion can be referred via an intercept mark mutual to setup if not altered by mistake redundantly.

Thus: Calculated area <=>12×6×9=27 cm2<=> \frac{1}{2} \times 6 \times 9 = 27\text{ cm}^2

The calculated area matches with the choice option:

  • The correct choice is 27 cm227 \text{ cm}^2, corresponding to provided option 4.

Therefore, the area of the deltoid is 27 cm2\boxed{27 \text{ cm}^2}.

Answer

27 27 cm².

Exercise #3

Given the deltoid ABCD

Find the area

555161616AAADDDCCCBBB

Video Solution

Step-by-Step Solution

To find the area of the deltoid ABCD, we use the external height formula for deltoids:

Given:
- Height (hh) = 1616 cm
- Segment related to base (bb) = 55 cm

The area of the deltoid can be calculated by:

Area=12×base×height\text{Area} = \frac{1}{2} \times \text{base} \times \text{height}

Plugging in our values, we have:

Area=12×5×16\text{Area} = \frac{1}{2} \times 5 \times 16

Calculating the result:

Area=12×80=40\text{Area} = \frac{1}{2} \times 80 = 40 cm2^2

Therefore, the area of deltoid ABCD is 4040 cm2^2.

Answer

40 40 cm².

Exercise #4

ACBD is a deltoid.

AD = AB

CA = CB

Given in cm:

AB = 6

CD = 10

Calculate the area of the deltoid.

666101010AAACCCBBBDDD

Video Solution

Step-by-Step Solution

To solve the exercise, we first need to remember how to calculate the area of a rhombus:

(diagonal * diagonal) divided by 2

Let's plug in the data we have from the question

10*6=60

60/2=30

And that's the solution!

Answer

30

Exercise #5

ABDC is a deltoid.

AB = BD

DC = CA

AD = 12 cm

CB = 16 cm

Calculate the area of the deltoid.

161616121212CCCAAABBBDDD

Video Solution

Step-by-Step Solution

First, let's recall the formula for the area of a rhombus:

(Diagonal 1 * Diagonal 2) divided by 2

Now we will substitute the known data into the formula, giving us the answer:

(12*16)/2
192/2=
96

Answer

96 cm²

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