## kellychick 3 years ago A crystal ball with a diameter of 2r inches is being packaged for shipment. If the crystal ball is placed inside a circular cylinder with radius r inches and height h inches, how much volume will need to be filled with padding? Assume r = 6, h = 12. (The volume of a sphere with radius r is 4πr3/3, and the volume of a right circular cylinder with radius r and height h is πr 2h.)

• This Question is Open
1. tcarroll010

Volume of cylinder - volume of sphere. Just substitute for r and h as is given in the problem.

2. crystal1

hey thats my name

3. kellychick

So then it would be 3.14*6^2*12?

4. tcarroll010

Start with the volume of the cylinder, whose formula is given to you in the problem, (π)(r)(2)(h). Can you make the substitutions for r and h that are given in the problem? Just saw your answer. That formula for the volume of a cylinder contains a factor of 2 x r, not r^2.

5. kellychick

okay so, (3.14)(6)(2)(12) should give you the answer correct?

6. tcarroll010

That's the volume of the cylinder, which is the first part. Read my first post for your next step.

7. kellychick

okay so i take that answer, and then subtract it from the volume of a sphere?

8. tcarroll010

The volume of a sphere is not 4πr3/3 as you have it in your problem statement. It's (4πr^3)/3. You're having a small problem with writing out the formula. Use either "^" for the exponent or the equation tool. And careful about which way you perform subtraction. That particular mathematical operation is not commutative, that is, a-b does not equal b-a.

9. kellychick

okay, well the volume of the sphere is 288. and the volume of a cylinder is 144..

10. tcarroll010

Better check your math on both of those volumes. I suggest writing out your work here (type it out) so I can see where you went wrong. Start with the volume of the cylinder.

11. kellychick

(pi)(6)(2)(12)=144

12. kellychick

or is it (pi)(6)^2(12) which would equal 432