Solve this application problem using a system of equations: 6000 is invested, part of it at 20% and part of it at 4%. For a certain year, the total yield is $800.00. How much was invested at 20%? How much was invested at 4%?
Let amount invested at 4% and 20% be F and T, respectively
Then we get: F + T = 6,000 ---- eq (i)
Also, .04F + .2T = 800 -------- eq (ii)
.2F + .2T = 1,200 ------ Multiplying eq (i) by .2 ----- eq (iii)
.16F = 400 ----- Subtracting eq (ii) from eq (iii)
F, or amount invested at 4% =