SOLUTION: Heather has a total of $5000 to invest. She puts part of it in an account paying 5%/year interest and the rest in a GIC paying 7.2% interest. If she has $349 in simple interest

Question 1131893: Heather has a total of $5000 to invest. She puts
part of it in an account paying 5%/year interest and the
rest in a GIC paying 7.2% interest. If she has $349 in
simple interest at the end of the year, how much was
invested at each rate?
what would the interest rate be at each percentage? Thank You!
Answer by greenestamps(13195) (Show Source): You can put this solution on YOUR website!

A setup for the traditional algebraic method of solving this kind of "mixture" problem....

Let x = amount invested at 5%
Then (5000-x) = amount invested at 7.2%

The total interest was $349:

I'll leave it to you to solve the equation to find the answer; the decimals might make things a bit ugly.

Here is a completely different way of solving this kind of problem -- much faster and easier than writing and solving an algebraic equation, if you understand the method and can do a little mental arithmetic.

(1) $349 interest on a total investment of $5000 makes the overall interest rate
.
or 6.98%

Comparing that interest rate to the individual rates of 5% and 7.2%, 6.98% is 9/10 of the way from 5% to 7.2%. (7.2-5 = 2.2; 6.98-5 = 1.98; 1.98/2.2 = 9/10).

That means 9/10 of the total was invested at the higher rate.

ANSWER: $4500 at 7.2%, $500 at 5%.
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