Problema Solution
Lilian has part of $9000 invested at 4% and the remainder at 6%. His annual return on each investment is the same. At what rate would she have to invest all her money to get the same interest?
Answer provided by our tutors
Let
x = the money invested at 4%
y = the money invested at 6%
x + y = 9000
0.04x = 0.06y (since his annual return on each investment is the same)
........
click here to see the system of equations solved for x and y
........
x = $5,400
y = $3,600
Let 'r' represent the rate that Lilian needs to invest to get the same interest:
9000r = 0.04*5,400 + 0.06*3,600
........
click here to see the equation solved for r
........
r = 0.048 or 4.8%
Lilian should invest all of her money at 4.8% to get the same interest.