Rectangle Area Problem: Calculate AB When Area = 44 and AC = 4

Q: How do I know which sides are length and width?

In a rectangle, opposite sides are equal. Since AC = 4, then BD = 4 too. Similarly, AB = CD. So AB and CD are one pair of equal sides, while AC and BD are the other pair.

Q: Why do we divide 44 by 4?

Because we know that Area = AB × AC. When we substitute: 44 = AB × 4. To find AB, we need to isolate it by dividing both sides by 4.

Q: What if I get a decimal answer?

That's completely normal! Rectangle problems can have whole numbers, decimals, or fractions as answers. Just make sure to check your work by multiplying back.

Q: Can I use AB × CD instead of AB × AC?

No! AB and CD are the same length (opposite sides of rectangle). You need to multiply different dimensions - one length times one width, like AB × AC.

Q: How do I remember the area formula?

Think of covering the rectangle with unit squares. If you have 11 squares across (AB) and 4 squares down (AC), you need 11 × 4 = 44 total squares!

Rectangle Area with Given Dimensions

The area of the rectangle below is equal to 44.

AC = 4

Calculate AB.

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations

00:00 Determine the value of AB

00:03 The formula for calculating the area of a rectangle is width(AB) multiplied by length(AC)

00:07 Substitute in the relevant values according to the given data and proceed to solve for AB

00:13 This is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution

Understand the problem

The area of the rectangle below is equal to 44.

AC = 4

Calculate AB.

Step-by-step solution

The area of the rectangle is equal to its length multiplied by its width.

Let's begin by substituting the known data into the formula:

$S=AB\times AC$

$44=AB\times4$

Let's now divide both sides by 4:

$AB=11$

Final Answer

Key Points to Remember

Essential concepts to master this topic

Formula: Rectangle area equals length times width (A = l × w)
Technique: Substitute known values: 44 = AB × 4, then solve
Check: Verify by multiplying: AB × AC = 11 × 4 = 44 ✓

Common Mistakes

Avoid these frequent errors

Confusing which sides to multiply
Don't randomly multiply any two numbers you see = wrong area calculation! Students often multiply the area by a given side instead of using the area formula correctly. Always identify length and width first, then use Area = length × width.

Practice Quiz

Test your knowledge with interactive questions

Look at the rectangle ABCD below.

Side AB is 6 cm long and side BC is 4 cm long.

What is the area of the rectangle?

FAQ

Everything you need to know about this question

How do I know which sides are length and width?

In a rectangle, opposite sides are equal. Since AC = 4, then BD = 4 too. Similarly, AB = CD. So AB and CD are one pair of equal sides, while AC and BD are the other pair.

Why do we divide 44 by 4?

Because we know that Area = AB × AC. When we substitute: 44 = AB × 4. To find AB, we need to isolate it by dividing both sides by 4.

What if I get a decimal answer?

That's completely normal! Rectangle problems can have whole numbers, decimals, or fractions as answers. Just make sure to check your work by multiplying back.

Can I use AB × CD instead of AB × AC?

No! AB and CD are the same length (opposite sides of rectangle). You need to multiply different dimensions - one length times one width, like AB × AC.

How do I remember the area formula?

Think of covering the rectangle with unit squares. If you have 11 squares across (AB) and 4 squares down (AC), you need 11 × 4 = 44 total squares!

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