SOLUTION: Paul has $30,000 to invest. His intent is to earn 15% interest on his investment. He can invest part of his money at 9% interest and part at 18% interest. How much does Paul need t

Question 1016203: Paul has $30,000 to invest. His intent is to earn 15% interest on his investment. He can invest part of his money at 9% interest and part at 18% interest. How much does Paul need to invest in each option to make a total 15% return on his $30,000?
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
x=9%
y=18% (can do this with one variable, too)
x+y=30,000
.09x+0.18(y)=.15*30,000=4500
============
x+y=30000
9x+18y=450000
-9x-9y=-270000, multiplying the top by -9
9y=180,000
y=20,000 @18%=$3600
x=10,000@9%=$900
They add to $4500.
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