SOLUTION: A certain sum of money is invested at 10%. Twice that amount is invested at 8%. The total amount of interest from both investments is $91. How much is invested at 8%?

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Question 204322: A certain sum of money is invested at 10%. Twice that amount is invested at 8%. The total amount of interest from both investments is $91. How much is invested at 8%?
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Let x = the amount invested at 10%, then 2x is the amount invested at 8%.
The interest earned on these two amounts can be expressed as:
0.1%28x%29%2B0.08%282x%29+=+91 Simplify the left side.
0.1x%2B0.16x+=+91
0.26x+=+91 Divide both sides by 0.26
x+=+350 and...
highlight%282x+=+700%29
$700 is invested at 8%