A sector containing an angle of 180o is cut off from a circle of radius 7 cm and folded into a cone. find the curved surface area of the cone (take π = 22/7)
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A sector containing an angle of 180° is cut off. It means a semicircle is cut off.
Radius = R = 7 cm.
Length of the curved arc part = 2 π R * 180°/360° = π R = 22/7 * 7 = 22 cm
After folding it into a cone, the curved part becomes the circumference
of the base of the cone.
Radius of the base of cone = r cm.
So 2 π r = 22 cm
r = 3.5 cm
Slanting height s of the cone is the radius of the bigger original circle.
So s = 7 cm.
CSA = curved surface area = π r s = 22/7 * 3.5 cm * 7 cm
= 77 cm²
Radius = R = 7 cm.
Length of the curved arc part = 2 π R * 180°/360° = π R = 22/7 * 7 = 22 cm
After folding it into a cone, the curved part becomes the circumference
of the base of the cone.
Radius of the base of cone = r cm.
So 2 π r = 22 cm
r = 3.5 cm
Slanting height s of the cone is the radius of the bigger original circle.
So s = 7 cm.
CSA = curved surface area = π r s = 22/7 * 3.5 cm * 7 cm
= 77 cm²
kvnmurty:
:-)
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3
I'm pretty sure the answer is 77m to the power of 2
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