A rectangle has two pairs of equal sides. We call the longer one length (l) and the shorter one width (w).
If you fill the rectangle with unit squares, you get wrows, each with lsquares. So the total is l × w. That's multiplication — much faster than counting one-by-one!
A 5 × 3 Rectangle — Count the Rows!
3 rows × 5 squares per row = 15 unit squares → area = 15 unit²
Area of a rectangle
Area = length × width = l × w
Worked Example
Find the area of a rectangle with length 8 cm and width 4 cm:
Step 1: Write the formula → Area = l × w
Step 2: Plug in → 8 × 4
Step 3: Calculate → 32 cm² ✓
🟫 Area of a Rectangle
Practice with the formula 📐
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1 Find the Area 📐
Use Area = l × w for each rectangle.
l = 6 cm, w = 2 cm
Area = 6 × 2 = cm²
l = 9 m, w = 4 m
Area = × = m²
l = 10 cm, w = 7 cm
Area = × = cm²
l = 12 m, w = 5 m
Area = × = m²
l = 15 cm, w = 8 cm
Area = cm²
l = 20 m, w = 11 m
Area = m²
🔁 Going Backwards
If you know the area and one side, divide!
Area = l × w ⇒ l = Area ÷ w and w = Area ÷ l
Example: Area = 24 cm², length = 6 cm → width = 24 ÷ 6 = 4 cm.
2 Find the Missing Side 🔍
Use division to find the missing length or width.
Area = 30 cm², l = 5 cm → w = cm
Area = 48 m², w = 6 m → l = m
Area = 56 cm², l = 8 cm → w = cm
Area = 72 m², w = 9 m → l = m
🟫 Area of a Rectangle
Real-world rectangles all around us! 🌍
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3 Word Problems 📝
Decide whether to multiply or divide, then solve.
A classroom floor is 9 m long and 6 m wide. What is its area?
Area = m²
A book cover is 25 cm long and 18 cm wide. How many cm² of paper covers it?
Area = cm²
A rectangular pool has an area of 60 m² and is 10 m long. How wide is it?
width = m
Reza is tiling a rectangular wall of 14 m by 3 m. How many m² of tiles does he need?
Area = m²
A piece of paper has area 100 cm² and width 5 cm. How long is it?
length = cm
⭐ Quick Check
A square is a special rectangle where length = width. So Area = s × s is just l × w with l = w!