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The perimeter of the ends of …

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The perimeter of the ends of the frustum of the cone are 207.24 cm and 169.56 cm .if the height of the frustum be 8 cm,find the whole surface area of the frustum .

  • 2 answers

Rashmi Bajpayee 7 years ago

At last, after multiplication the answer is not 7392.52.

The correct answer is 7592.52 sq.cm

Naveen Sharma 7 years ago

Ans. Let R and r be the radii of two ends of frustum.

Then

{tex}=> 2\times 3.14 \times R = 207.24{/tex}

=> R = 33 cm

{tex}=> 2\times 3.14 \times r = 169.56{/tex}

=> r = 27 cm

Height of frustum h = 8cm

Slant Height of Frustum l = {tex}\sqrt {(R-r)^2 + h^2}{/tex}

{tex}\sqrt {(33-27)^2+(8)^2} = \sqrt {36+64}{/tex}

=> 10

TSA of frustum = {tex}\pi l(R+r) +\pi R^2 +\pi r^2{/tex}

=> {tex}\pi [l(R+r) + R^2+r^2]{/tex}

=> {tex}3.14[10(33+27) + 1089 + 729]{/tex}

=> 3.14[600+1089+729]

=> 3.14 (2418)

=> 7392.52cm2

 

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