Question 12

The area of the base of a right circular cone is $$40\pi$$ andits height is 15 cm. The curved surface area of the cone (in $$cm^2$$) is:

Solution

Base of a right circular cone = $$400\pi$$
2$$\pi$$r = $$40\pi$$
r = 20
h = 15
$$l^2 = r^2 + h^2$$
$$l^2 = (20)^2 + (15)^2$$
$$l^2 = 400 + 625$$
$$l^2 = (25)^2$$
l = 25
The curved surface area of the cone = $$\pi rl =\pi \times 20 \times 25$$ = 500$$\pi $$


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