---
title: "The Missing Side"
description: "Learning video: Half of 18 is 9. 9 minus 5 is 4. The rectangle is 4 centimeters wide. A rectangle has a perimeter of 30 cm and is 9 cm long. How wide is it?"
canonical: "https://www.mathapex.app/en/math-stories/geometry/the-missing-side/"
language: "en"
video: "https://www.mathapex.app/media/stories/videos/en/the-missing-side.83e90a2d.mp4"
duration: "PT38S"
---

# The Missing Side

Learning video 83 · Geometry · Grade 4 · 0:38

## Read the story

A rectangle has a perimeter of 18 centimeters. It is 5 centimeters long.

How wide is it? One length plus one width is exactly half the way around.

Half of 18 is 9.

9 minus 5 is 4. The rectangle is 4 centimeters wide.

**A rectangle has a perimeter of 30 cm and is 9 cm long. How wide is it?**

## Answer and working

Correct! Half of 30 is 15. 15 minus 9 is 6 centimeters.

`30 ÷ 2 − 9 = 6`