You are here:

Calculus/Integration applications.

Advertisement


gabe wrote at 2008-12-01 23:43:50
your response is incorrect.



pi(r^4) = kt + c

when t = 0, r = 1, therefore c = pi this is true



but



when t = 15, r = 2, c = pi



16pi = 15k + pi

15k = 15pi

k = pi



k does not equal one




starfish wrote at 2010-02-23 23:26:22
just gotta say whoever wrote the first answer and said



15pi = 15k



and then



k = 1



totally throwin me off.



which changes the answer that the second person got (80pi) to just plain 80


gallagherg wrote at 2011-01-13 01:37:44
the above answer is partially wrong.



15pi = 15k  (this is from Above)



k does not equal one



k equals pi




supahgeek wrote at 2011-05-02 02:17:36
actually, FYI, k=pi because 15(pi) divided by 15 equals pi, and 15k divided by 15 equals k, so k=pi.


Richard Evans wrote at 2012-03-06 19:11:17
I believe there is major mistake made in the solution of this problem.



In the steps solving for k the following was shown:



         16 pi = 15k + pi



         15 pi = 15k



         k = 1



The answer for k should be pi not 1.




whit wrote at 2012-04-17 01:56:56
For part (a)  when you were solving for k, you had:



15 pi=15 k



but you had k=1. k actually equals pi. (k=pi)**



so the answer would end up being (for a):



pi r^4=pi t + pi

r^4=(pi t+pi)/pi

r^4=t+1



r=(t+1)^1/4  


paragon wrote at 2014-02-07 02:34:10
I think you may have made a mistake. C/pi = C. Therefore in r^4= (kt +c)/pi simplifies to r^4= (kt/pi) + c. Plug in values of t=0 and r=1, 1= (k(0))/pi + c, c=1.


alias wrote at 2016-06-02 00:39:19
For part A, everything is correct up until

15 pi = 15k



k = 1



The correct answer is k = pi



Therefore the answer to part A is r = (t + 1)^1/4 after some simplifying



This will also change the answer of part B simply to t = 80


Calculus

All Answers


Answers by Expert:


Ask Experts

Volunteer


Paul Klarreich

Expertise

All topics in first-year calculus including infinite series, max-min and related rate problems. Also trigonometry and complex numbers, theory of equations, exponential and logarithmic functions. I can also try (but not guarantee) to answer questions on Analysis -- sequences, limits, continuity.

Experience

I taught all mathematics subjects from elementary algebra to differential equations at a two-year college in New York City for 25 years.

Education/Credentials
(See above.)

©2016 About.com. All rights reserved.