Question 107577
First let's deal with the area of the hemisphere dome.  The surface area of a sphere is given by {{{4*pi*r^2}}}, but this is a hemisphere, so we only need half of that, or {{{2*pi*r^2}}}.


Since we only need to compute to the nearest square foot, {{{pi=3.14}}} should be a close enough approximation. Since the dome fits on top of the 10 foot radius cylinder, the hemisphere radius must also be 10 feet.


{{{2*3.14*100=628ft^2}}} 


The cylinder part is easy if you consider cutting it all the way up the side and then flattening it out so that you will have a rectangle that is the cylinder altitude on one side and the cylinder circumference on the other.


Since {{{C=2*pi*r}}}, the circumference of the cylinder is 62.8 ft.


Then the surface area of the cylinder must be {{{24*62.8=1507.2}}}


Adding the cylinder surface to the dome surface and rounding gives:


{{{628 + 1507= 2135ft^2}}}  rounded to the nearest square foot.


Each gallon of paint covers {{{300ft^2}}}, so {{{G=2135/300}}} which is 7.12 gallons, but rounded UP is 8 gallons.