SOLUTION: Phyllis invested $12,000, a portion earning a simple interest rate of 4.5% per year and the rest earning a rate of 4% per year. After 1 year the total interest earned on these inv
Question 816750: Phyllis invested $12,000, a portion earning a simple interest rate of 4.5% per year and the rest earning a rate of 4% per year. After 1 year the total interest earned on these investments was $525. How much did she invest at each rate?
I am constantly getting this answer wrong. The book is saying 30, but when I follow the equation
0.04x +0.045(12000-x)=525
my answer is way off. Maybe I'm working out the wrong equation. Found 2 solutions by ewatrrr, rothauserc:Answer by ewatrrr(24785) (Show Source): You can put this solution on YOUR website!
Hi,
Investing $12,000, some at 4% and some at 4.5%
0.04x +0.045(12000-x)= $525
0.04x + 540 -.045x = 525
540-525 = .005x
15/.005 = x = $3000 at 4% and $9000 at 4.5%
CHECKING our answer*** = $120 + $405 = $525
Answer by rothauserc(4718) (Show Source): You can put this solution on YOUR website! simple interest is calculated with this formula I = prt, where p is principal, r is rate and t is time,
in this case t is 1 year
0.04x +0.045(12000-x)=525 is setup correctly
0.04x +540 -0.045x = 525
-0.005x = -15
x = 3000
The problem asks us how much money was invested at 4% and 4.5% given that Phyllis had $12,000 to invest. Our calculation shows the following
$3,000 invested at 4%
$9,000 invested at 4.5%
We are also told that Phyllis earned $525 in interest from both investments
now check the answers
0.04*3000 + 0.045*9000 = $120 + $405 = $525
our answers check