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    				| 1. | 
                                    A hemispherical tank is made up of an iron sheet 1 cmthick. If the inner radius is 1 m,then find the volume of the iron used to make the tank | 
                            
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Answer» Inner radius `(r_(1))=1m=100 cm` Outer radius `(r_(2))=(100+1)cm " " (because` inner radius + thickness) = 101 cm Outer volume `=(2)/(3)pi(101)^(3) " " (because "volume" =(4)/(3)pi r^(3))` Inner volume `=(2)/(3)pi(100)^(3)` Hence, volume of the iron used to make the tank = outer volume - inner volume `= (2)/(3)pi[(101)^(3)-(100)^(3)]` `=(2)/(3)xx(22)/(7)(101-100)[(101)^(2)+101xx100+(100)^(2)]` `=(2)/(3)xx(22)/(7)(10201+10100+10000)` `=(44)/(21)(30301)=63487.80 cm^(3)` `=(63487.80)/(100xx100xx100)m^(3)=0.063 m^(2)` (approx.)  | 
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