when r = 30 cm and s = 80 cm.
Find the surface area of the ENTIRE cone shown here please

Question

when r = 30 cm and s = 80 cm.
Find the surface area of the ENTIRE  cone shown here please

anonymous · Answer

attachment

hartnn · Answer

find the height 'h' first!
using pythagoras theorem

anonymous · Answer

ok , will do this now

hartnn · Answer

h = $\sqrt {80^2-30^2}$

hartnn · Answer

or you can directly use the formula 
$\large A = \pi r(r+s)$

anonymous · Answer

yes so h= 85.44  or   $$10\sqrt{73}$$

hartnn · Answer

and for area ?

hartnn · Answer

how come h is greater than 80 ?

anonymous · Answer

sorry my bad  h= 74.161 
and 
A= 3.14 x 30 (30+80)  =  10362  square cm

hartnn · Answer

$s^2=h^2+r^2$
and i got 10367 using the google calculator...
u have choices ?

anonymous · Answer

is this correct ?

anonymous · Answer

yes the choices are

 A) 10,306 square centimeters
 B) 10,362 square centimeters
 C) 11,362 square centimeters
 D) 12,306 square centimeters

hartnn · Answer

yes, then 10362 is correct :)

anonymous · Answer

so its B 
thanks  a lot @hartnn  for your help :)

hartnn · Answer

welcome ^_^