Question

Paul has $70,000 to invest. His intent is to earn 15% interest on his investment. He can invest part of his money at 8% interest and part at 18% interest. How much does Paul need to invest in each option to make a total 15% return on his $70,000?

Answer 1

Let n be the part invested at 18%. Then:
.18n+.06(40000-n)=.15(40000)
.18n+2400-.06n=6000
.12n=3600
n=3600/.12=$30000 at 18%, $10000 at 6%!!!!!!!!!!!!!