Area and Perimeter • Topic 1 of 6

Rectangles

A rectangle’s area is length × width, and its perimeter is 2(length + width). Area is measured in square units and counts the space inside; perimeter is a length and measures the distance around the edge. The single most common error is using the wrong one — multiplying when the question wants the distance around, or adding when it wants the space inside. Read whether the question asks for area or perimeter, then apply the matching formula. You can also work backward: given the area and one side, divide to find the other; given the perimeter and one side, solve 2(l + w) for the unknown.

A rectangle of length 8 and width 5Rectangle85Area = 8 × 5 = 40    Perimeter = 2(8+5) = 26

✅ Solved examples

1. A rectangle is 8 by 5. Find its area.
8 × 5 = 40.
2. A rectangle is 8 by 5. Find its perimeter.
2(8 + 5) = 26.
3. A rectangle has area 48 and width 6. Find its length.
48 ÷ 6 = 8.
4. A rectangle is 12 by 7. Find its area.
12 × 7 = 84.

✏️ Practice — try these, take hints as needed

1. A rectangle is 9 by 4. Find its area.
length × width.
9 × 4.
—
36.
2. A rectangle is 10 by 6. Find its perimeter.
2(l + w).
2(16).
—
32.
3. A rectangle has area 30 and length 6. Find its width.
30 ÷ 6.
—
—
5.
4. A rectangle is 11 by 3. Find its area.
11 × 3.
—
—
33.
5. A rectangle is 7 by 7. Find its perimeter.
2(7 + 7).
—
—
28.

📝 Topic test — 8 questions

Auto-graded with full solutions; saved to your dashboard. Use the calculator and formula sheet (top-right) any time.

Loading questions…
Squares →