looks like you've written the clues in question yourself..
according to the question (we let r be the radius and h be the height of the cylinder)
4*2πr(squared)=2πrh
4r=h
r=28/4
r=7
so the radius is 7cm
which means the radius of the hemisphere is 7cm
and the height of the hemisphere is also 7cm
so the total height is 28+7=35 Ans!
