SOLUTION: An investment at 8% and some at 9% annual simple interest. The interest for 1 year on the combined investment of $10,000 was $840. How much was invested at each rate? Write a syst

Algebra ->  Percentage-and-ratio-word-problems -> SOLUTION: An investment at 8% and some at 9% annual simple interest. The interest for 1 year on the combined investment of $10,000 was $840. How much was invested at each rate? Write a syst      Log On


   

Question 839243: An investment at 8% and some at 9% annual simple interest. The interest for 1 year on the combined investment of $10,000 was $840. How much was invested at each rate? Write a system of two equations in two variables to solve each problem.
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

Re: reply. One needs to solve the system of EQs by substitution to find x and y.

Write a system of two equations in two variables to solve each problem.

Let x and y represent amount saved at 8% and 9% respectively

    x  + y = $10,000    0r  x = $10,000 - y 

 .08x + .09y = $840

 .08(10,000 - y) + .09y = 840  |solving the system of EQs by substitution

             .01y = 840-800

              .01y = 40

                 y = $4000  and x = $6000