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 May 12, 2020
 #1
avatar+111326 
+1

First one

 

Volume  = (1/3) pi r^2 * h   =  (1/3) pi (3^2) * 9  =  81 pi cm^3

 

Surface area  =  pi *r * l    +  pi * r^2

 

Note  that   l  =   √[3^2 + 9^2]  =  √90  = 3√10

 

So we have

 

Surface area  =  pi * r   [ l  + r]  =  pi * 3 * [ 3√10 + 3] =  pi * 3 * 3 [ √10 + 1] = 9 [ √10 + 1] pi  cm^3

 

 

cool cool cool

 May 12, 2020

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