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Topic: need help to solve algebra problem
Replies: 4   Last Post: May 31, 2005 8:47 AM

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Barb Knox

Posts: 578
Registered: 12/6/04
Re: need help to solve algebra problem
Posted: May 31, 2005 7:21 AM
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In article <d7hecb$p4u$>,
"lionel vulliemin" <> wrote:

>Good morning, I come swiss, and hoe that someone could help me with this
>we have 2 summ put in an account for a total of 20.000 $ .
>the first have t%, and give 1.080 $ interest par year.
>the second have (t+1)% , and it give 800 $ par year.
>find the two capital ?
>I don't now how to find the result ! on the book, it's writing the first one
>have a capital of 12.000$, and the second have 8.000$...... could you give
>me the way to find these 2 capitals.
>Thank you very much

Firstly, check the book answer; if you can't do that then either the book is
wrong (possible but unlikely) or you don't adequately understand the problem:
$12000 * t/100 = $1080, so t must = 9; then
$ 8000 * (9+1)/100 should = 800, which it does.
So, the book answer checks.

Now, setting up the equations, let x the capital amount at the t% rate;
then (20000 - x) is the amount at the (t+1)% rate, so
x * t/100 = 1080; and
(20000 - x) * (t+1)/100 = 800.
This is 2 equations in 2 unknowns, which you should be able to reduce to 1
equation in 1 unknown by substitution (by solving the first equation for x
or for t -- your choice).

Then solve that final equation (which will be a quadratic) for its 1
unknown, and use that value in the first equation to calculate the other

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