A rectangle has a length that is twice its width. If the perimeter of the rectangle is 36 units, what is the width of the rectangle?

February 22, 2026

How to Solve Rectangle Problems: Finding the Width When Length is Double the Width

Understanding basic geometry principles helps solve many problems involving rectangles—especially when dimensions follow simple ratios. One common question is: If a rectangle has a length that is twice its width and a perimeter of 36 units, what is the width? This article breaks down the math behind the problem with clear steps, making it easy for students and math enthusiasts alike.

Understanding the Rectangle’s Dimensions

A rectangle has two consistent measurements: length and width. According to the problem, the length is twice the width. We can express this relationship using algebra:

Let the width = w Then the length = 2w

Using the Perimeter Formula

The perimeter P of a rectangle is calculated with the formula: P = 2 × (length + width)

Substituting the values we have: 36 = 2 × (2w + w)

Simplify inside the parentheses: 36 = 2 × (3w) 36 = 6w

Solving for the Width

To find w, divide both sides of the equation by 6: w = 36 ÷ 6 w = 6

Verifying the Answer

We now know the width is 6 units. Since length = 2 × width, the length is: 2 × 6 = 12 units

Calculate the perimeter to confirm: P = 2 × (12 + 6) = 2 × 18 = 36 units, which matches the given value.

Final Answer

The width of the rectangle is 6 units.

Why This Problem Matters

Solving for unknown dimensions in geometric shapes helps build foundational skills in algebra and practical math. Whether in architecture, design, or daily planning, recognizing how ratios and formulas work together can simplify complex problems effortlessly.

If you’re studying geometry or preparing for exams, mastering problems like this strengthens logical thinking and equation-solving abilities.

Quick Recap:

Let width = w, length = 2w
Perimeter = 2 × (length + width) = 36
Substitute: 2 × (2w + w) = 36 → 6w = 36 → w = 6

You’ve now learned a simple but powerful method to find unknown rectangle dimensions—guaranteed to boost your confidence in math!

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