Preserved Topic: Ahhh! Help with son's Algebra homework

Could one of the many math wizards that I know keep residence here at the Asylum please help my son and I figure out the solution to this problem? No matter which way we try to work it out, we can't seem to get it.

quote:

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Rockjaw invested part of his savings at 7% and the rest at 13%. The amount at 7% was $200 more than the amount at 13%. If his total return after one year was $84, find the amount invested at each rate.

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Assume that the interest rates indicate annual simple interest.

Man, it's been a long time since high school and I didn't pay quite as much attention in algebra class as I should have.

Oh... could you please show your work .

Thanks everybody

-Butcher-

(x+200)0.07 + 0.13x = 84

0.07x + 0.13x + 14 = 84

0.20x = 70

x = 350

invested 350 at 13% and 550 at 7%

or maybe not...
been a loooong time since I did any math...

[This message has been edited by ZOX (edited 12-11-2001).]

Thanks ZOX!!

We were close but we weren't doing the (x+200)0.07 part correctly.

We were doing

0.07 + 200 + 0.13 = 84

without the ().

Thanks again

-Butcher-

Sometimes it helps to use "let" statements so you don't have to think of the whole equation at once...

let x equal the amount invested at 13%
let x + 200 equal the amount invested at 7%

(x+200)*.07 + .13*x = 84

and you know the rest.