A liquid filter shaped as a right circular cone is shown below.

Question

anonymous · Answer

attachment

anonymous · Answer

If a similar cone has a slant height of 15 cm, what is its lateral area?

 90π cm2

 150π cm2

 75π cm2

 120π cm2

anonymous · Answer

Similar means the measurements are in proportion, right?

anonymous · Answer

And a quick web search gives: http://math.about.com/od/formulas/ss/surfaceareavol_2.htm So we need SA = pi r^2 + pi r s where s is the slant height. OK?

anonymous · Answer

d?

anonymous · Answer

?

anonymous · Answer

Here

anonymous · Answer

Do you understand the formula for the surface area.  Unless I'm misunderstanding what is meant by "lateral area"

anonymous · Answer

so im wrong

anonymous · Answer

Oh, that's what the d? meant.  I have to calculate, sorry.

anonymous · Answer

r = (15/20) times 8 = 
r = 6
s = 15
SA = pi r^2 + pi r s
  = pi 36 + pi 90 
  = 126 pi

anonymous · Answer

Hmm..  Do you see an error anywhere.  Think I'm good.

anonymous · Answer

not an answer ?
 90π cm2

 150π cm2

 75π cm2

 120π cm2

anonymous · Answer

Yes. Is the formula for lateral area somehow wrong? Or the answers? These guys have the same formula http://www.web-formulas.com/Math_Formulas/Geometry_Surface_of_Cone.aspx

anonymous · Answer

i doubt its the answers

anonymous · Answer

Call for backup.  Maybe someone can find an error.