Problema Solution
Piotr invested some money at 3.5% simple interest, and $5000 more than three times this amount at 4%. He earned $1440 in annual interest. How much did he invest at each rate?
Answer provided by our tutors
Let
x = the money invested at 3.5% simple interest
3x + 5000 = the money invested at 4% simple interest
He earned $1440 in annual interest:
0.035*x + 0.04*(3x + 5000) = 1440
........
click here to see the equation solved for x
........
x = $8,000
3x + 5000 = 3*8000 + 5000 = $29,000
Piotr invested $8,000 at 3.5% and $29,000 at 4%.