Question 180200
find the radius of a cone given the surface area and slant height. round to the nearest tenth T=359ft^2 , l=15 ft
:
the surface area formula: SA = {{{pi*r*sqrt(r^2+h^2)}}}
Where
r = radius
h = altitude 
;
However we are given the slant height (l):
l = {{{sqrt(r^2+h^2)}}}
so we can just substitute l for that in the formula
SA = pi * r * l
so we have:
pi * r * 15 = 359
r = {{{359/(15*pi)}}}
r = 7.618 ~ 7.6 ft