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The radius of the base of …

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The radius of the base of right circular cylinder is increased by 75 percent and height is decreased by 50 percent . Find the percent change in curved surface area

Posted by Premlata Awasare 8 years, 9 months ago

CBSE > Class 09 > Mathematics

1 answers

Naveen Sharma 8 years, 9 months ago

Ans. Let old radius of cylinder = r

old Height of clyinder = h

old CSA of Cylinder = {tex}2\pi r h{/tex}

New radius of cylinder = {tex}r + {75\times r \over 100} = {7r\over 4}{/tex}

New height of cylinder = {tex}h - {h\times 50\over 100} = {h\over 2}{/tex}

New CSA of Cylinder = {tex}2\times \pi\times {7r\over 4}\times {h\over 2} {/tex}

{tex}={ 7\pi rh \over 4}{/tex}

Change (decrease) in CSA ={tex}2\pi rh - { 7\pi rh \over 4} = {\pi rh \over 4}{/tex}

% decrease = {tex}{\pi rh \over 4 \times 2 \pi rh }\times 100 = 12{1\over 2}\%{/tex}

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