
Differential Equations Ordinary and Partial Differential Equations Math Forum 
 LinkBack  Thread Tools  Display Modes 
August 24th, 2017, 06:20 AM  #1 
Senior Member Joined: Oct 2015 From: Antarctica Posts: 128 Thanks: 0  Provided solution isn't simplified and is wrong?
Observe the following problem: Notice that the answer doesn't seem right. Shouldn't K be C*(4*pi)*(3/(4*pi))^(2/3) rather than C*((4*pi*3)/(4*pi))^(2/3)? Or am I wrong and I don't understand? If this answer isn't wrong, then why isn't it simplified? What's going on here? This was the provided answer key by my instructor. Last edited by John Travolski; August 24th, 2017 at 06:41 AM. 
August 24th, 2017, 06:49 AM  #2 
Math Team Joined: Jul 2011 From: North America, 42nd parallel Posts: 3,372 Thanks: 233 
You are correct , probably a typo. The exponent should be between the parenthesis and bracket. 
August 24th, 2017, 06:57 AM  #3 
Senior Member Joined: Oct 2015 From: Antarctica Posts: 128 Thanks: 0 
Thanks, I appreciate the reassurance.

August 24th, 2017, 09:52 AM  #4 
Global Moderator Joined: Dec 2006 Posts: 19,287 Thanks: 1681 
Any sphere of radius r has volume ∝ r³ and surface area ∝ r², so dV/dt = cV$^{2/3}$, where c is a positive constant and V is the raindrop's volume at time t. The above assumes that the raindrop's rate of evaporation means the raindrop's rate of change of volume. 

Tags 
provided, simplified, solution, wrong 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
What did I do wrong in my solution?  davedave  Differential Equations  2  June 28th, 2017 09:01 AM 
What is wrong with my solution? (Series Exercise)  babaliaris  Calculus  3  August 28th, 2016 03:08 AM 
What's wrong with my solution ?  szz  Differential Equations  3  December 28th, 2014 07:18 PM 
what's wrong with my solution?  dennisdixon  Algebra  1  January 17th, 2013 11:09 PM 