Question

If the volume of a sphere is 18 cm cubed, what is the radius?

Answer 1

V = 4/3 pi r^3. find r from that.

Answer 2

Volume = 4/3 pi r^3
find r using that formula.

Answer 3

omg but i need to know the radius.

Answer 4

And you can find it, just work backwards. Plug in the volume you are given and solve for r.

Answer 5

the equation for the volume of a sphere is (4*Pi*r)/3
solve for r by moving 3/(4*pi) to the other side of the equation
so you get r^3 = (3*18)/(4*pi)
simplify

Answer 6

what?

Answer 7

if V = 4/3 pi r^3,
then multiply both sides by 3/4
3/4V = pi r^3
divide both sides by pi
r^3 = (3/4pi) V
r = cube root of (3/4 pi) V, substitute V = 18 for your answer.
Also, learn manipulation of equations.
http://www.chem.tamu.edu/class/fyp/mathrev/mr-algeb.html

Answer 8

khanacademy.org has good videos demonstrating how to do this.