Can someone please explain how to do this? I need a memory refresh because it slipped my mind over the summer.



A man invested $6000, part of it at 5% simple interest and the rest at 7% simple interest. If his annual interest income is $372, how much did he invest at each rate?

Well, you know he invested $6000 at two rates, and he got $372 in interest. Let the amount at one rate be equal to x; the amount at the second rate, then, is 6000-x, because it's the total ($6000) minus the amount at the other rate (x). Then just solve for x. Your equation should look something like this:

$372 = .07x + .05(6000-x)

Hmm.. alright. So is it $36.00 ?

Oops hold on, I`m not done...

that`s for 5% right? how do i figure out the 7%?

Well, if you solve the expression in the parentheses, you will find that:

372 = .07x + 300 - .05x

So now you just solve for x.

Once you get x, you're not done; you know that x amount was invested at 7%, and 6000 (the total) was invested at 5%; so x was invested at 5%, and 6000 - x was invested at 7%.