Mensuration Help(Cylinder + hemsiphere)?

Question

Please help
A shape consist of two identical hemispheres on either side of a right cylinder. The total area is 1800 pi and the height of the cylinder is 30. Find the common base radius.

Thanks

Answer 1

4 pi r^2+2 pi r * h =1800 pi
4r^2+60r-1800=0
or

r^2+15r-450=0


r1={-15+sqrt(225+1800) }/2

={-15+sqrt(2025)}/2
=(-15+45)/2=30/2=15

radius length must be positive

ANSWER: 15

Answer 2

let r=common base radius, then
2x2pi r^2+2pirx30=1800pi
r^2+15r=450
r^2+15r-450=0
(r-15)(r+30)=0
r=15ANS.