Surface Area of Cylinders

Question

Mr. Jenkins has cylindrical columns and rectangular prism posts on his front porch.  Both have a height of 3.5 feet.  The columns have a radius of 0.5 feet.  The prisms have a length and width of 1.25 feet.  There are four columns and 2 posts.  Mr. Jenkins wants to paint the lateral areas of all the columns and posts.  How many square feet does Mr. Jenkins have to paint?  If Mr. Jenkins can paint about 30 square feet in an hour, how long will it take him to complete the work? 

Answer 1

Cylindrical columns have the surface area of the circumference (2*pi * radius) times the height of the cylinder. rectangular prisms have the surface area perimeter of the base (twice the length plus twice the height) times height. (top and bottoms don't count).

 

So four columns means 4*(2*pi*.5*3.5)=43.96

four prism posts means 2*(2*1.25+2*1.25)*3.5=35

total surface area=35+43.96=78.96/30=2.6 hours.

 

Hope that helps,

Deanna

Answer 2

79ft^2 in about 2.5hours