Calculate Rectangle Perimeter: Finding Distance Around ABCD with Sides 7 and 10

Q: Why can't I just use 7 and 10 to find the perimeter?

The number 10 represents only part FC, not the complete side DC of rectangle ABCD. Without knowing the missing segment DF, we can't determine the full length of side DC.

Q: What information would I need to solve this problem?

You would need two complete adjacent sides of rectangle ABCD. For example, if you knew the full length DC or the width AB, you could then calculate the perimeter.

Q: How do I know when I have enough information for a rectangle perimeter?

For any rectangle, you need at least two adjacent sides (length and width). Then use the formula: $ P = 2(length + width) $

Q: Is 'It is not possible to know' ever a correct answer in math?

Yes! In geometry problems, sometimes insufficient information is given intentionally. Always check if you have all the measurements needed before attempting calculations.

Q: What's the difference between the two rectangles shown?

Rectangle AEFD (left) and rectangle EBCF (right) are separate rectangles that share a common side EF. The question asks about the larger rectangle ABCD, which contains both smaller rectangles.

Rectangle Perimeter with Insufficient Information

What is the perimeter of the given rectangle ABCD?

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations

00:00 Calculate the perimeter of the rectangle

00:04 Opposite sides are equal in a rectangle

00:21 The whole side equals the sum of its parts

00:34 We don't have sufficient data to determine the perimeter

00:38 This is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution

Understand the problem

What is the perimeter of the given rectangle ABCD?

Step-by-step solution

In the statement, we have two rectangles that are connected by a common side,

The left quadrilateral, AEFD, has a known side - AD

The right quadrilateral, EBCF, also has only one known side: FC

In the question, we are asked for the perimeter of the rectangle ABCD,

For this, we need its sides, and since the opposite sides in a rectangle are equal, we need at least two adjacent sides.

We are given the side AD, but the side DC is only partially given.

We have no way of finding the missing part: DF, so we have no way of answering the question.

This is the solution!

Final Answer

It is not possible to know

Key Points to Remember

Essential concepts to master this topic

Perimeter Formula: Rectangle perimeter requires both length and width measurements
Given Information: Only side AD = 7 is known, DC is partially shown as 10
Check Requirements: Need complete dimensions of all four sides to calculate perimeter ✓

Common Mistakes

Avoid these frequent errors

Assuming the partial measurement represents the full side
Don't add 7 + 10 = 17 or use 2(7 + 10) = 34 thinking these are complete sides! The 10 only represents part FC, not the full side DC. Always verify you have complete measurements for both adjacent sides before applying the perimeter formula.

Practice Quiz

Test your knowledge with interactive questions

Look at the rectangle below.

Side DC has a length of 1.5 cm and side AD has a length of 9.5 cm.

What is the perimeter of the rectangle?

FAQ

Everything you need to know about this question

Why can't I just use 7 and 10 to find the perimeter?

The number 10 represents only part FC, not the complete side DC of rectangle ABCD. Without knowing the missing segment DF, we can't determine the full length of side DC.

What information would I need to solve this problem?

You would need two complete adjacent sides of rectangle ABCD. For example, if you knew the full length DC or the width AB, you could then calculate the perimeter.

How do I know when I have enough information for a rectangle perimeter?

For any rectangle, you need at least two adjacent sides (length and width). Then use the formula: $P = 2(length + width)$

Is 'It is not possible to know' ever a correct answer in math?

Yes! In geometry problems, sometimes insufficient information is given intentionally. Always check if you have all the measurements needed before attempting calculations.

What's the difference between the two rectangles shown?

Rectangle AEFD (left) and rectangle EBCF (right) are separate rectangles that share a common side EF. The question asks about the larger rectangle ABCD, which contains both smaller rectangles.

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