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Question
The internal and external diameters of a hollow hemi-spherical vessel are 21 cm and 28 cm respectively. Find: total surface area.
Solution
External radius (R) = 14 cm
Internal radius (r) =`21/2` cm
Total surface area =
`2piR^2+2pir^2+pi(R^2-r^2)`
= `693+1232+22/7((14)^2-(21/2)^2)`
=`1925+22/7(196-441/4)`
`=1925+22/7xx343/4`
= 1925 + 269.5
= 2194.5 cm2
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