SOLUTION: 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

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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) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = amount invested @ 5%
Let +b+ = amount invested @ 9%
———————
(1) +a+%2B+b+=+40000+
(2) +%28+.05a+%2B+.09b+%29%2F40000+=+.06+
—————————————————
Solve for a and b. I’d do it, but it’s bedtime
Cheers

Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!

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!