Question

Phyllis invested $10,000, a portion earning a simple interest rate of 5 1 5 % per year and the rest earning a rate of 5% per year. After one year the total interest earned on these investments was $512.00. How much money did she invest at each rate?

Answer 1

I assume 5 1 5 is 5.15%

Explanation:

If we invest `$x` at 5.15% `=>x xx 1.0515=$1.0515x`

The rest, `$(10000-x)`, is invested at 5% `=>$(10000-x)1.05`

`=$10500-1.05x`

These two add together to make $10512

`1.0515x+10500-1.05x=10512`

`1.0515x-1.05x=10512-10500`

`0.0015x=12`

`x=12/0.0015`

x=8000

10000-8000=2000

$8000 at 5.15% and $2000 at 5%