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Question -

The perimeters of the ends of a frustum of a right circular cone are 44 cm and 33 cm. If the height of the frustum be 16 cm, find its volume, the slant surface and the total surface.



Answer -

Given,

Perimeter of the upperend = 44 cm

2 π r1 =44

2(22/7) r1 =44

r= 7cm

Perimeter of the lowerend = 33 cm

2 π r2 =33

2(22/7) r2 =33

r=21/4 cm

Now,

Let the slant heightof the frustum of a right circular cone be L

L = 16.1 cm

So, the curved surfacearea of the frustum cone = π(r1 + r2)l

= π(7 + 5.25)16.1

Curved surface area ofthe frustum cone = 619.65 cm3

Next,

The volume of thefrustum cone = 1/3 π(r22 + r12 +rr)h

= 1/3 π(72 +5.252 + (7) (5.25) ) x 16

= 1898.56 cm3

Thus, volume of thecone = 1898.56 cm3

Finally, the totalsurface area of the frustum cone

= π(r1 +r2) x L + π r12 + π r22

= π(7 + 5.25) × 16.1 +π7+ π5.252

= π(7 + 5.25) ×16.1 + π(72 + 5.252) = 860.27 cm2

Therefore, the totalsurface area of the frustum cone is 860.27 cm2

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