Geometry Basics

Area and Perimeter

Compute rectangle area A = l × w and perimeter P = 2(l + w) for l = 8, w = 5.

Example

Substitute rectangle dimensions into area and perimeter formulas.

highlighted = computed this step

Step 1 — Rectangle dimensions

Set up the given values.

l=8w=5l= 8 \quad w= 5
Rectangle with length 8 and width 5.length 8width 5A = 8 x 5 = 40P = 2 x 13 = 26Dimensions label the sides before choosing a formula.

Step 2 — Area formula

Use A = l x w: 8 x 5 = 40.

A=8×5=40A= 8 \times 5 = \hl{40}
Area fills the inside: 8 x 5 = 40.length 8width 540 square unitsA = 8 x 5 = 40P = 2 x 13 = 26The inside has 40 square unit cells.

Step 3 — Add length and width

Add length and width first: 8 + 5 = 13.

8+5=138 + 5 = \hl{13}
One length plus one width: 8 + 5 = 13.length 8width 58 + 5 = 13A = 8 x 5 = 40P = 2 x 13 = 26One corner path has length 13.

Step 4 — Perimeter formula

Use P = 2(l+w): 2 x 13 = 26.

P=2×13=26P= 2 \times 13 = \hl{26}
Perimeter is the boundary: 2 x 13 = 26.length 8width 5boundary length 26A = 8 x 5 = 40P = 2 x 13 = 26The full boundary uses two lengths and two widths.

Step 5 — Result

Read the final result.

A=40P=26A= 40 \quad P= 26
Area 40; perimeter 26.length 8width 5boundary length 2640 square unitsA = 8 x 5 = 40P = 2 x 13 = 26Area counts inside squares; perimeter counts boundary length.
area-and-perimeter For a rectangle with length l and width w: - Area = l × w (square units). - Perimeter = 2 × (l + w) (total edge length).