The height of a right circular cone is 4cm. The radius of its base is 3cm. Find the curved surface area
A
\(9\pi cm^2\)
B
\(15\pi cm^2\)
C
\(16\pi cm^2\)
D
\(20\pi cm^2\)
Verified Correct Answer: B.
Step-by-Step Mathematical Solution
Curved surface area or a cone \(=\pi rl\)
from the information \(l^2 = 4^2 + 3^2 = 16+9\\
l = \sqrt{25} = 5; ∴ C.S.A\hspace{1mm} = \frac{22}{7}\times 3 \times 5\\
Since \frac{22}{7}=\pi ∴ C.S.A\hspace{1mm} =\hspace{1mm}15\pi\)
Source: Myschool Past Questions Archive (Record #26513)