Question

MS. Blackmon invested $8000, part at 4% and the rest at 5% per year. How much did she invest at each rate if her total return per year on the investments was $380?

Answer 1

I = PxRxT

I = Interest money created

P = Principal

R = Rate per year in decimal

T = time in years

Blackmon obtained 380 of investing P dollars at 5% and (8000 - P) dollars at 4%, this means:

380 = (8000 - P) (0.04)(1) + (P)(0.05)(1) = (8000 - P)(0.04) + P (0.05)

380 = 320 - 0.04P + 0.05P = 320 + 0.01P

380 - 320 = 0.01P

60 = 0.01P

P = 60/0.01

P = 6000

So he invested 6000 dollars at 5%

and (8000 - 6000) = 2000 dollars at 4%

Answer:

$6,000 at 5%

$2,000 at 4%