Login

Search the forums now!

Welcome, Guest. Please login or register.

November 01, 2025, 03:06:14 pm
Pages: [1]   Go Down

Author Topic: multi variable integration  (Read 892 times)  Share 

0 Members and 1 Guest are viewing this topic.

Chavi

  • sober since 1992
  • Victorian
  • Part of the furniture
  • *****
  • Posts: 1413
  • "Death to the juice"
  • Respect: +5
multi variable integration
« on: May 29, 2010, 07:14:05 pm »
0
Hey, could I please get some help with the following question:

A partly filled tank contains 200 liters of pure water in which 1500 grams of salt have been dissolved. Waters in poured in at 6 L/min. The mixture is kept uniform by stirring, and leaves that tank at 5L/min.

Find an expression for x grams of salt in terms of time, t.


Logged
2009: Math Methods CAS [48]
2010: English [47]|Specialist Maths[44]|Physics[42]|Hebrew[37]|Accounting[48]  atar: 99.80
My blog: http://diasporism.wordpress.com/

Yitzi_K

  • Victorian
  • Forum Leader
  • ****
  • Posts: 893
  • Respect: +3
Re: multi variable integration
« Reply #1 on: May 29, 2010, 07:37:49 pm »
0
Use this formula.


conc stands for concentration of salt.
Logged
2009: Legal Studies [41]
2010: English [45], Maths Methods [47], Economics [45], Specialist Maths [41], Accounting [48]

2010 ATAR: 99.60

theuncle

  • Victorian
  • Trailblazer
  • *
  • Posts: 36
  • Respect: +1
Re: multi variable integration
« Reply #2 on: May 29, 2010, 07:40:43 pm »
0
I tried to use a differential equation and got
not sure if it's right though
Logged

Chavi

  • sober since 1992
  • Victorian
  • Part of the furniture
  • *****
  • Posts: 1413
  • "Death to the juice"
  • Respect: +5
Re: multi variable integration
« Reply #3 on: May 29, 2010, 08:11:15 pm »
0
Quote from: Yitzi_K on May 29, 2010, 07:37:49 pm
Use this formula.


conc stands for concentration of salt.

Right, but how do you integrate the expression (as contains 2 variables)?
Logged
2009: Math Methods CAS [48]
2010: English [47]|Specialist Maths[44]|Physics[42]|Hebrew[37]|Accounting[48]  atar: 99.80
My blog: http://diasporism.wordpress.com/

theuncle

  • Victorian
  • Trailblazer
  • *
  • Posts: 36
  • Respect: +1
Re: multi variable integration
« Reply #4 on: May 29, 2010, 10:57:47 pm »
0













my first post was without the formula which involved considerably more working, hence i only posted the answer.

Will this kind of question be on the specialist exam?
Logged

TrueTears

  • TT
  • Honorary Moderator
  • Great Wonder of ATAR Notes
  • *******
  • Posts: 16363
  • Respect: +667
Re: multi variable integration
« Reply #5 on: May 30, 2010, 06:18:35 pm »
0
Quote from: Chavi on May 29, 2010, 08:11:15 pm
Quote from: Yitzi_K on May 29, 2010, 07:37:49 pm
Use this formula.


conc stands for concentration of salt.

Right, but how do you integrate the expression (as contains 2 variables)?
You are not using multi variable integration to solve differential equations, what theuncle done is correct, using separable differential equations to solve the DE.

Multivariable integration requires integrating over an surface which kinda requires you to visualize the surface.
Logged
PhD @ MIT (Economics).

Interested in asset pricing, econometrics, and social choice theory.
Pages: [1]   Go Up