# Thread: Help with volume formula

1. ## Help with volume formula

The volume of water a spherical tank can hold is given by the next formula:

$V(h)= \pi h^2 \frac{3R - h}{3}$

, where:

● V is the water volume inside the tank in $m^3$
● R is the radius in $m$, and
● h is the level of water, measured from the bottom of the tank (in $m^3$).

I need to find out, using bisection and Newton-Raphson iterations, what the level of water has to be in order to get $90m^3$ of water from a $3m$ radius tank.

So basically, what i've done is find the value of $h$ within the formula, and apply bisection to the resulting equation. But here's the problem. The resulting formula is a 3º degree formula, so i get 3 roots (obviously bisection gives me just one, depending on the initial interval).

So the three roots are (aprox.):
$7.4526264$
$4.2565863$
$- 2.7092127$