Total Surface Area of Cone


 
 
Concept Explanation
 

Total Surface Area of Cone

Total Surface Area of Cone:

Total surface area of cone = Curved surface area + Area of the base =pi r^{2}+pi rl=pi r(r+l)

Illustration: Find the total surface area of a cone, if its slant height is 12 m and the radius of its base is 9 m.

Solution: We know that the total surface area S of a right circular cone of radius r and slant height l is given by S= large  pi rl+pi r^2=pi r(l+r).

Here, r = 9 m and  l = 12 m. 

Therefore large dpi{80} large S= pi r(l+r)=frac{22}{7} times 9 times (12 +9)=frac{22}{7} times 9 times 21 = 594m^2

Illustration: The total surface area of a cone is =60pi ;cm^{2}. If the slant height of the cone be 8 cm, find the radius of the base.

Solution: Given: Area of the curved surface of a cone is =60pi ;cm^{2}. and slant height of the cone = 8 cm

Also, we know that the Total surface area of the cone =pi r^{2}+pi rl =pi r(r+l)

                                 60pi= pi r(r+l)

                                60= r(r+l)

As l = 8, hence we have

60= r(r+8)

60= r^{2}+8r

r^{2}+8r-60=0

r=frac{-8pm sqrt{64+240}}{2}

r=frac{-8pm sqrt{304}}{2}

r=frac{-8pm 4sqrt{19}}{2};cm

As r cannot be negative, So we must have

r=frac{-8+ 4sqrt{19}}{2};cm

Hence, radius of the base is  frac{-8+ 4sqrt{19}}{2};cm                                              

Sample Questions
(More Questions for each concept available in Login)
Question : 1

Find the total surface area of a right circular cone with radius 6 cm and slant height 8 cm.

Right Option : C
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Explanation
Question : 2

Find the total surface area of the cone if the slant height is 3.5 cm and the radius of the base is 14 cm.

Right Option : B
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Explanation
Question : 3

Find the total surface area of a cone, if its slant height is 21 m and the diameter of its base is 24 m.

Right Option : A
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Explanation
 
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