## Solving for 'P' in simple interest problem.

Quadratic equations and inequalities, variation equations, function notation, systems of equations, etc.

### Solving for 'P' in simple interest problem.

Hi,
I've been stuck on this one problem the entire day.

Question: If an amount P is invested at simple annual interest rate r, then the amount A available at the end of t years is given by A=P+Prt. Solve for P, in terms of A, t and r.

The closest solution I have has been:
A=P+Prt
A/P=(P+Prt)/P
A/P=rt

but, finding how to remove or move the A from the P side of the problem has been an ongoing adventure.

Have a Great day,
Trent
Trent

Posts: 2
Joined: Sun May 31, 2009 1:05 am

Trent wrote:...A=P+Prt. Solve for P, in terms of A, t and r.

The closest solution I have has been:
A=P+Prt
A/P=(P+Prt)/P
A/P=rt

How did you get that P/P equalled zero...?

Try being a little more explicit in your steps when solving literal equations:

. . . . .$A\, =\, P\, +\, Prt$

Factor out the variable $P:$

. . . . .$A\, =\, P(1\, +\, rt)$

Then divide through by everything non-$P:$

. . . . .$\frac{A}{1\, +\, rt}\, =\, P$

stapel_eliz

Posts: 1703
Joined: Mon Dec 08, 2008 4:22 pm

### Re: Solving for 'P' in simple interest problem.

Thank you Very much!

I have been out of Algebra for Many years...and apparently, it shows.

Taking an intermediate algebra for a much needed refresher course.
Trent

Posts: 2
Joined: Sun May 31, 2009 1:05 am