Grade 9 · Lesson 23
Area of shapes
Six shapes, six formulas — explore how length, height, and radius change the area you cover.
A = l × wA = s²A = ½ × b × hA = b × hA = ½(a + b)hA = πr²
What is area?
Area measures how much surface a shape covers — counted in square units (cm², m², …). Stretch a dimension, and the covered region grows.
Rectangle
Length times width — the classic tiling of unit squares.
A = l × w
8
5
Area equation
A = l × w
A = 8 × 5 = 40
40square units
Formula card
Keep these six identities handy — tap a card to open that explorer.
Mixed practice
All six shapes — work carefully, then check. Include units mentally; type the number only.
Question 1 of 8
RectangleA rectangle is 8 cm long and 5 cm wide. Find its area.
Lesson 23 · Area of shapes · Grade 9
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