SOLUTION: The Pacific Investment Group invested some money in an account that earns 7.6% annual simple interest. Twice the amount invested at 7.6%, was invested in a second account that earn

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Question 1075124: The Pacific Investment Group invested some money in an account that earns 7.6% annual simple interest. Twice the amount invested at 7.6%, was invested in a second account that earns 3.9% annual simple interest. If the total annual interest earned from the two investments was $3080, how much was invested at 7.6% (that is, in the first account?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
for simple interest,
+I+=+P%2Ar%2At+
They are talking about annual interest, so
+t+=+1+
----------------
For account earning 7.6% interest:
+I%5B1%5D+=+P%2A.076%2A1+
+I%5B1%5D+=+.076P+
For account earning 3.9% interest:
+I%5B2%5D+=+2P%2A.039%2A1+
+I%5B2%5D+=+.078P+
----------------------------
+I%5B1%5D+%2B+I%5B2%5D+=+3080+
+I%5B1%5D+%2B+I%5B2%5D+=+.076P+%2B+.078P+
+I%5B1%5D+%2B+I%5B2%5D+=+.154P+
+.154P+=+3080+
+P+=+20000+
--------------------
$20,000 was invested @ 7.6% interest
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check answer:
+I%5B1%5D+=+.076P+
+I%5B1%5D+=+.076%2A20000+
+I%5B1%5D+=+1520+
and
+I%5B2%5D+=+.078P+
+I%5B2%5D+=+.078%2A20000+
+I%5B2%5D+=+1560+
and
+I%5B1%5D+%2B+I%5B2%5D+=+1520+%2B+1560+
+I%5B1%5D+%2B+I%5B2%5D+=+3080+
OK