Question

A cylindrical tank if 8 ft. in diameter and 20 ft tall. how many gallons of paint are needed to paint the tank if one gallon covers 200 sq ft ?

and

a cylindrical hole with diameter 8 inches is cut through a cube 10 in. on a side. find the surface area of this solid

HOW PLEASE. huhu please help. just tell me how pleaaaase.

Answer 1

the area is 2πr(r+h)
since 1 gallon covers 200ft^2, just divide the area by 200
Note r=4,h=20
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Assuming the axis of the cylinder is parallel to an edge of the cube, what you have is just a cylinder where r=4 and h=10

area is figured as above, so the answer is 1/2 the value obtained above.