# Thread: Volume of Sphere

1. ## Volume of Sphere

A spherically shaped balloon is being inflated so that the radius is changing at a constant rate of 2 in./sec. Find an algebraic representation for V(t), the volume in terms of time, t.

Would this be the right algebraic equation, $V(t) = \frac {4}{3} \pi (2t + r)^3$ ?

2. Adding r inside the parentheses is redundant because r=2t. You see what I mean? So everything is right, but I would write the eqaution like this:

V(t)=(4/3)(pi)(2t)^3

Does that help you at all?

3. Originally Posted by VonNemo19
Adding r inside the parentheses is redundant because r=2t. You see what I mean? So everything is right, but I would write the eqaution like this:

V(t)=(4/3)(pi)(2t)^3

Does that help you at all?
Well if "r" is the original radius of the balloon, wouldn't you need the variable when it is at 0 seconds.

4. I doubt that the problem requires previous Knowlege of the original radius. I mean, It's a balloon. It could be laying down flat before it was inflated, or possibly wrinkled. Yeah, maybe, but if I was your teacher, the answer I gave you is the one I would be looking for.

5. Originally Posted by VonNemo19
I doubt that the problem requires previous Knowlege of the original radius. I mean, It's a balloon. It could be laying down flat before it was inflated, or possibly wrinkled. Yeah, maybe, but if I was your teacher, the answer I gave you is the one I would be looking for.
Ok thanks alot. I'm gonna ask my teacher to clarify it just to make sure, but thanks.