Question 346274
a cylindrical chemical storage tank must have a height 4 meters greater than 
the radius of the top of the tank.
 Determine the radius of the top and the height of the tank if the tank must
 have a volume of 15.71 cubic meters.
:
Let r = the radius of the tank
It says,"must have a height 4 meters greater than the radius." therefore
(r+4) = the height of the tank
:
Volume of a cylinder: V = {{{pi*r^2*h}}}
Therefore
{{{pi*r^2*(r+4)}}} = 15.71
divide both sides by pi, results
r^2(r+4) = {{{15.71/pi}}}
r^3 + 4r^2 = 5
r^3 + 4r^2 - 5 = 0 
just from looking at this you know that r=1, then the height = 5
:
:
Check this
 V = {{{pi*1^2*(1+4)}}}
 v = 15.707 ~15.71