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May 29th, 2012, 03:53 PM  #1 
Member Joined: May 2012 Posts: 34 Thanks: 0  help me, differential equation
When mixing a certain alcoholic beverage, a barperson starts with a 10 litre solution of 20% alcohol. Into this solution the barperson mixes a 40% alcohol mixture at the rate of 1 litre/minute and pours into glasses at the rate of 2 litres/minute. (a) Find a formula for the volume V (t) of the mixture at time t minutes. (b) Find a differential equation that tells the rate of change of the amount of alcohol A(t) at time t minutes. (c) Solve the differential equation and use the initial condition to find a formula for A(t) dont know hard qs, can u help me 
May 29th, 2012, 09:59 PM  #2 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs  Re: help me, differential equation
There's no need to bump a topic after a few hours. It will be seen and someone will come along and help. If after a few days no one does, then its okay to bump it, preferably with some work or thoughts on how to proceed. 
May 29th, 2012, 10:02 PM  #3 
Member Joined: May 2012 Posts: 34 Thanks: 0  Re: help me, differential equation
sorry but i am doing my practice now and want to finish

May 29th, 2012, 10:04 PM  #4 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs  Re: help me, differential equation
Post your thoughts about what you should do, and when I log on tomorrow, I promise I will help. 
May 29th, 2012, 10:42 PM  #5 
Member Joined: May 2012 Posts: 34 Thanks: 0  Re: help me, differential equation
ok i wait for u 
May 30th, 2012, 04:43 AM  #6 
Member Joined: May 2012 Posts: 34 Thanks: 0  Re: help me, differential equation
This is as good as i can think please help me dy/dt= the rate of flow in  rate of flowing out so flow in is 2/5 litre alcohol says the question and flow out is 2y(t)? so dy/dt+2y(t)=2/5? 
May 30th, 2012, 07:18 AM  #7 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs  Re: help me, differential equation 
May 30th, 2012, 11:37 AM  #8 
Member Joined: May 2012 Posts: 34 Thanks: 0  Re: help me, differential equation
i tried but my work is very big confusion can u show me steps to do part a.b.c

May 30th, 2012, 12:13 PM  #9 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs  Re: help me, differential equation
a) Let V be measured in liters and t be measured in minutes. We are given the IVP: where Hence, we have: We may now use the given initial condition to determine C: thus: b) Let A be measured also in liters. We are given: where Write the ODE in standard linear form: c) Now we compute the integrating factor: Multiplying the ODE by the integrating factor gives: We may now use the given initial condition to determine C: thus: 

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