Question 1122414:  Paul has $40,000 to invest.  his intent is to earn 6% interest on his investment.  He can invest part of his money at 5% and part at 9% interest.  How much does Paul need to invest in each option to make a total of 6% return on his $40,000?  I don't even know where to start with this.  I have no clue how to put this into equation form.  I would appreciate a little help.  THANK YOU!!! 
 Found 2 solutions by  josmiceli, MathTherapy: Answer by josmiceli(19441)      (Show Source):  Answer by MathTherapy(10557)      (Show Source): 
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Paul has $40,000 to invest.  his intent is to earn 6% interest on his investment.  He can invest part of his money at 5% and part at 9% interest.  How much does Paul need to invest in each option to make a total of 6% return on his $40,000?  I don't even know where to start with this.  I have no clue how to put this into equation form.  I would appreciate a little help.  THANK YOU!!! 
Let amount that he needs to invest at 5% be F 
Then amount he needs to invest at 9% is: 40,000 - F 
We then get the following EARNINGS equation: .05F + .09(40,000 - F) = .06(40,000) 
.05F + 3,600 - .09F = 2,400 
.05F - .09F = 2,400 - 3,600 
- .04F = - 1,200 
F, or amount he needs to invest at 5% =   
Amount he needs to invest at 9% =   
You need to do your own check!  
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