Area Calculation: Finding Parallelogram Area Using Rectangle Area of 35 cm²

Parallelogram Areas with Rectangle Relationships

ABCD is a parallelogram and AEFD is a rectangle.

AE = 7

The area of AEFD is 35 cm².

CF = 2

What is the area of the parallelogram?

S=35S=35S=35777222AAAEEEDDDFFFCCCBBB

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Determine the area of the parallelogram ABDC
00:04 Apply the formula for the area of a rectangle: side(AE) multiplied by side(ED)
00:11 Insert the relevant values into the forma and proceed to solve for ED
00:14 Isolate ED
00:19 This is the length of side ED
00:26 Opposite sides are equal in a rectangle
00:30 The whole side equals the sum of its parts
00:41 Apply the formula for the area of a parallelogram
00:44 height(ED) multiplied by base(CD)
00:47 Insert the relevant values into the formula and proceed to solve for the area
00:50 This is the solution

Step-by-step written solution

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1

Understand the problem

ABCD is a parallelogram and AEFD is a rectangle.

AE = 7

The area of AEFD is 35 cm².

CF = 2

What is the area of the parallelogram?

S=35S=35S=35777222AAAEEEDDDFFFCCCBBB

2

Step-by-step solution

Let's first calculate the sides of the rectangle:

AEDF=AE×ED AEDF=AE\times ED

Let's input the known data:

35=7×ED 35=7\times ED

Let's divide the two legs by 7:

ED=5 ED=5

Since AEDF is a rectangle, we can claim that:

ED=FD=7

Let's calculate side CD:

2+7=9 2+7=9

Let's calculate the area of parallelogram ABCD:

ABCD=CD×ED ABCD=CD\times ED

Let's input the known data:

ABCD=9×5=45 ABCD=9\times5=45

3

Final Answer

45 cm².

Key Points to Remember

Essential concepts to master this topic
  • Rectangle Formula: Area equals length times width to find missing dimensions
  • Technique: Use 35=7×ED 35 = 7 \times ED to find ED = 5 cm
  • Check: Parallelogram area = 9 × 5 = 45 cm² matches rectangle base ✓

Common Mistakes

Avoid these frequent errors
  • Using rectangle area as parallelogram area
    Don't assume the parallelogram ABCD has the same area as rectangle AEFD = 35 cm²! The parallelogram extends beyond the rectangle by CF = 2 cm, making it larger. Always calculate the full base length: AF + FC = 7 + 2 = 9 cm.

Practice Quiz

Test your knowledge with interactive questions

A parallelogram has a length equal to 6 cm and a height equal to 4.5 cm.

Calculate the area of the parallelogram.

6664.54.54.5

FAQ

Everything you need to know about this question

Why isn't the parallelogram area the same as the rectangle area?

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The parallelogram ABCD extends beyond the rectangle AEFD by the length CF = 2 cm. So while they share the same height, the parallelogram has a longer base (9 cm vs 7 cm).

How do I find the height of the parallelogram?

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The height is the same as the rectangle's width! Since Area = length × width for the rectangle, we get ED=357=5 ED = \frac{35}{7} = 5 cm.

What if the diagram looks confusing with all the shapes?

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Focus on what you know: The rectangle AEFD gives you the height (ED = 5), and you can find the full base by adding AF + FC = 7 + 2 = 9 cm.

Can I use a different formula for parallelogram area?

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Yes! You can use Area=base×height Area = base \times height where the height is perpendicular to the base. Here, ED = 5 is perpendicular to the base CD = 9.

How do I know which measurements to use?

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For parallelogram area, you need a base and its corresponding height. The rectangle shows that ED = 5 is the height, and CD = AF + FC = 9 is the base.

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