Answer
4000 dollars must be invested at 6%.
Work Step by Step
Let X represent the amount of money invested at 6%.
We receive 6% $\times$ X = 0.06X from this investment.
From the 2000 dollars invested at 3% we receive:
3% $\times$ 2000 = 60 dollars
The average return is 5%.
Both investments equal 2000 + X, so we can set up the following equation:
0.06X + 60 = .05 $\times$ (2000 + X)
0.06X + 60 = 100 + 0.05X
0.01X = 40
Divide both sides by 0.01:
X = 4000
4000 dollars must be invested at 6%.
