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What is the surface are of a right circular cone if the cone's diameter is 10cm and the lenght is 20cm.

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HElp please.
asked Mar 18, 2014 in ALGEBRA 2 by chrisgirl Apprentice

1 Answer

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The diameter (d ) of right circular cone is 10 cm and its length (h ) is 20 cm.

Lateral Surface Area of right circular cone : A = πrs = πr * sqrt (r2 + h2),

where r = radius of the base (circle) = d/2 = 10/2 = 5 cm.

          h = height of the cone = 20 cm.

          s = slant height = sqrt (r2 + h2) = sqrt (52 + 202) =  sqrt (25+ 400) =  sqrt (425) =  √425 cm

  and  π = 3.14.

Lateral Surface Area of right circular cone : A = πrs = 3.14 * 5 * √425 = 3.14 * 5 * 20.61 = 323.66 cm2

Total Surface Area of right circular cone : A = πr2 + πrs.

A = (3.14 * 52) + (3.14 * 5 * √425)

A = (3.14 * 25) + (3.14 * 5 * 20.61).

A = 78.5 + 324.6075

A = 403.1075 cm2.

Lateral surface area of right circular cone is 323.66 cm2 and its total surface area is 403.1075 cm2.

answered Mar 22, 2014 by rob Pupil
edited Mar 22, 2014 by rob

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