Geometry · Perimeter & area · 3.2

Area of rectangles.

Area is the space inside a shape, measured in square units. For a rectangle, area is length × width. An 8 × 5 rectangle covers 40 square units. (A square is just l = w, so area = side².)

01 / THE IDEA

See it work.

The figure

See the shape.

85

Watch the method

Area of rectangles

Area of a rectangle = l × w (square = s²).

1 / 2
1

Area of a rectangle

Area is length times width.

l×wl \times w
2

Multiply

Multiply the two dimensions.

8×5=408 \times 5 = 40
02 / YOUR TURN

Practice until it feels automatic.

Your turn

Find the measure.

Type the number — units optional.

streak 0
best 0

…

— / WHY IT WORKS

The idea underneath.

Count the squares

Area tiles the inside with unit squares: rows × columns = l × w.

Why it works

8 across, 5 down → 40 squares.

03 / WORKED EXAMPLES

From easy to tricky.

EX 1easy

Area of a 14×9 rectangle?

1

Area of a rectangle

Area is length times width. l × w

2

Multiply

Multiply the two dimensions. 14 × 9 = 126

EX 2medium

Area of a 10×9 rectangle?

1

Area of a rectangle

Area is length times width. l × w

2

Multiply

Multiply the two dimensions. 10 × 9 = 90

EX 3hard

Area of a 5×8 rectangle?

1

Area of a rectangle

Area is length times width. l × w

2

Multiply

Multiply the two dimensions. 5 × 8 = 40

04 / COMMON TRAPS

Where students slip.

Trap

Adding instead of multiplying.

Fix

Area multiplies; perimeter adds.

Trap

Forgetting square units.

Fix

Area is in square units.

05 / QUIZ

Test yourself.

The Test

12 problems across three tiers. Auto-graded on submit. Hints and a full walkthrough on every question. Your work is saved on this device — sign in to keep it across devices.

0/12Answered
How to answerType just the value. Formatting won't trip you up — we ignore spaces, capital letters, commas, and subscript style, so t₁ = 5, d = 3 and t1=5,d=3 both count. For a list of numbers, separate them with commas (e.g. 3, 10, 17).
Core

Core (4)

C1

Area of a 3×9 rectangle?

Need a hint?
  • Multiply length × width.
  • A square is side × side.
C2

Area of a 9×7 rectangle?

Need a hint?
  • Multiply length × width.
  • A square is side × side.
C3

Area of a 5×3 rectangle?

Need a hint?
  • Multiply length × width.
  • A square is side × side.
C4

Area of a 7×4 rectangle?

Need a hint?
  • Multiply length × width.
  • A square is side × side.
Apply

Apply (4)

A1

Area of a 7×3 rectangle?

Need a hint?
  • Multiply length × width.
  • A square is side × side.
A2

Area of a 8×13 rectangle?

Need a hint?
  • Multiply length × width.
  • A square is side × side.
A3

Area of a 11×12 rectangle?

Need a hint?
  • Multiply length × width.
  • A square is side × side.
A4

Area of a 12×13 rectangle?

Need a hint?
  • Multiply length × width.
  • A square is side × side.
Extension

Extension (4)

E1

Area of a 11×14 rectangle?

Need a hint?
  • Multiply length × width.
  • A square is side × side.
E2

Area of a 11×3 rectangle?

Need a hint?
  • Multiply length × width.
  • A square is side × side.
E3

Area of a 13×14 rectangle?

Need a hint?
  • Multiply length × width.
  • A square is side × side.
E4

Area of a 7×14 rectangle?

Need a hint?
  • Multiply length × width.
  • A square is side × side.