The simple interest per year is given by the following formula:
Where:
P= initial amount
r= rate
t= time
Where: prt is the annual interest.
Therefore:
We know that:
Also:
Replacing:
Secondly:
Isolating P1 in (2):
Substituing (3) in (1):
Finally, puttin P2=6,000 in equation (3):
Answer: The amount she invest at each rate is $14,00 at 4% and $6,000 at 9.5%.