college algebra word problem

Question

Use a system of linear equations with two variables and two equations to solve.

If an investor invests a total of $40,000 into two bonds, one that pays 4% simple interest, and the other that pays 3 7/8% interest, and the investor earns $1581.25 annual interest, how much was invested in each account?

Answer 1

4(X)+3.78Y = 1581.25

X = 400-Y

4(400-Y) + 3.78Y = 1581.25

1600-4Y + 3.78Y = 1581.25

0.22Y =18.75

Y = 18.75/.22 = 85 = $8,500 approximately at 3.78%

X = 400-85 = 315 = $31,500 at 4%

The $1581 interest is 3.9525%. 1581/40000

3.9525 is more than twice as close to 4% than to 3.85%, so much more of the investment will be at 4%