Q1
The curved surface area of a cylinder is:
A2πrh
Bπr²h
C6 x side²
Dπrl
CBSEClass 9 (CBSE)MathematicsCh 11 · Topic 1
Surface Area of Solids
Learning to calculate the surface area of common 3-D solids.
Core concept
Understanding the distinction between curved (or lateral) surface area and total surface area is important — curved surface area excludes flat top/bottom surfaces (useful for problems like painting only the side of a cylindrical tank), while total surface area includes all surfaces. These formulas have direct practical applications in manufacturing, packaging design, and construction, where the amount of material needed to cover a 3-D object's surface must be calculated precisely.
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Quick notes
• Cube surface area: 6 x side². Cuboid: 2(lb+bh+hl).
• Cylinder curved surface area: 2πrh. Total surface area adds 2πr² for the two circular ends.
• Cone curved surface area: πrl (l = slant height).
• Curved/lateral surface area excludes flat ends; total surface area includes all surfaces.