# Word problem with differential equations?

• Mar 28th 2014, 12:04 PM
canyouhelp
Word problem with differential equations?
Am having trouble with finding the equations for word problems of differential equations. Did I get these two right? Attachment 30549 If not, which one is right for the problem?
• Mar 29th 2014, 06:54 PM
HallsofIvy
Re: Word problem with differential equations?
If that is all you want to know, then the first is wrong, the second is right.

If you want to know why the first is wrong and the second right, you will need to tell us why you thought they were correct.
• Mar 30th 2014, 06:22 AM
canyouhelp
Re: Word problem with differential equations?
Quote:

Originally Posted by HallsofIvy
If that is all you want to know, then the first is wrong, the second is right.

If you want to know why the first is wrong and the second right, you will need to tell us why you thought they were correct.

Okay, I just redid the first one and got the same answer :/. I used the compounding formula: A=p(1+r)^n For this it would be: B=50(1 + 0.05/12)^12t And subtracting the money put in by the mom. Wouldn't that give me A?
• Mar 31st 2014, 05:34 AM
hollywood
Re: Word problem with differential equations?
I must be missing something - the first term is the interest - 0.05B/12 (monthly interest times principal). Mom puts in 240/6 = 40 a month, and Saleem takes out 50 a month, so that gives -10 for the other term. So isn't A correct?

- Hollywood
• Mar 31st 2014, 06:01 AM
canyouhelp
Re: Word problem with differential equations?
Quote:

Originally Posted by hollywood
I must be missing something - the first term is the interest - 0.05B/12 (monthly interest times principal). Mom puts in 240/6 = 40 a month, and Saleem takes out 50 a month, so that gives -10 for the other term. So isn't A correct?

- Hollywood

I thought so! I wasn't extremely sure but after writing it all out that's what I had. Thanks :)