Answer
2000
Work Step by Step
He invests 4000 at 4% interest and and invests some other amount
(x that we have to calculate) at 5.5% interest so that the interest he receives each year is 4.5% of the total amount invested (4000 + x).
4000$\times$0.04 + 0.055x=(4000+x)$\times$0.045
160+0.055x=180+0.045x now subtract 0.045x
0.01x=20 divide by 0.01
x=2000
