Let the radius of the solid hemisphere=r units.
`therefore` the volume of the solid hemisphere `=(2)/(3)pir^(3)` cu. Units and its whole surface area `=3pir^(2)` sq.units.
As per question ,`(2)/(3)pir^(3)=3pir^(2) rArr r=(9)/(2)=4.5`
Hence the radius of the solid hemisphere =4.5 units.