Lesson 5: Geometric Measurement: Area & Perimeter

Property

The perimeter of a rectangle is calculated using the formula $P = 2 \times (l + w)$, where $l$ is the length and $w$ is the width.
To find an unknown side length (e.g., width $w$) when the perimeter $P$ and length $l$ are known, you can use the formula:

Examples

Property

The area ($A$) of a rectangle is the product of its length ($l$) and width ($w$), calculated with the formula $A = l \times w$. To find a missing side length when the area is known, you can rearrange this formula using division: $l = \frac{A}{w}$ or $w = \frac{A}{l}$.

Examples

Property

To solve for a final area ($A_{new}$) or perimeter ($P_{new}$) after a multiplicative comparison, follow these steps:

1. Find the unknown dimension of the original shape (e.g., $w_{original} = \frac{A_{original}}{l_{original}}$).
2. Calculate the new dimensions using the scaling factor (e.g., $l_{new} = k \times l_{original}$).
3. Calculate the final area or perimeter using the new dimensions (e.g., $A_{new} = l_{new} \times w_{new}$).

Examples