The external radius of the hemisphere is 6 cm and the thickness of it is 2cm.
`therefore` internal radius of the hemisphere =(6-2) cm =4 cm.
`therefore` the whole surface area of the hemisphere lt brgt =`(2pixx6^(2)+2pixx4^(2)+pixx6^(2)-pixx4^(2))` sq.cm
`= pi(2xx36+2xx16+36-16) ` sq.cm
`=(22)/(7)xx(72+32+20) "sq.cm" =(22)/(7)xx124 "sq.cm"=(1728)/(7) "sq.cm"=389(5)/(7)`sq.cm.
Hence the whole surface area of the hemisphere `=389(5)/(7)` sq,cm.
