How much money did she invest at each rate?

Question

Phyllis invested $10,500, a portion earning a simple interest rate of 5 1/5% per year and the rest earning a rate of 5% per year. After 1 year the total interest earned on these investments was $538. $ at 5 1/5% $ at 5%

Answer 1

Let B = the amount at the higher rate and L = the amt at the lower rate

The sum of B and L is the total amount invested = 10500

 

.052B = the interest from the higher rate investment and .05L = the interest from the smaller

The total interest = .052B + .05L = 538

 

B + L = 10500

.052B + .05L = 538 => 52B + 50L = 538000

 

B = 10500 - L

Substitute : 52(10500 - L) + 50L = 538000

 

546000 - 2L = 538000

2L = 8000

L = 4000 and B = 6500