# Homework Help: Calculus Related Rates Interesting Problem

1. Oct 25, 2009

### Gregarious101

1. The problem statement, all variables and given/known data

http://www.kent.k12.wa.us/pcpow/questions/calc/0401trickortreat/index.html [Broken]

This is an old problem, and I have been able to solve one and two, I believe the answers are

1. pi cm/second
2. 50(pi) cm^3/second
3. This is the one I am not sure of. How can I solve this? Isn't there two many variables?

2. Relevant equations

V=4/3(pi)r^3
dV/dt= 2(pi)r^2
dC/dt= (2(pi))*cube root(V/(4/3(pi)))*(1/(4/3(pi)))*(dV/dt)

3. The attempt at a solution

I am getting lost at three, the rest are pretty easy, I think.

THANK YOU!!

Last edited by a moderator: May 4, 2017
2. Oct 25, 2009

### tiny-tim

Welcome to PF!

Hi Gregarious101! Welcome to PF!

(have a pi: π and try using the X2 tag just above the Reply box )
Just do it the other way …

The circumference is increasing at a rate of 1/8 cm per second: if it starts empty, what its it after five minutes?