SOLUTION: Two certificates of deposit pay interest at rates that differ by 4%. Money invested for one year in the first CD earns $270 interest. The same principal invested in the other CD ea

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Question 1070841: Two certificates of deposit pay interest at rates that differ by 4%. Money invested for one year in the first CD earns $270 interest. The same principal invested in the other CD earns $450. Find the two rates of interest.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +r+ = rate of interest for 1st CD
Let +P+ = the principal for both CDs
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(1) +r%2AP+=+270+
(2) +%28+r+%2B+.04+%29%2AP+=+450+
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(1) +P+=+270%2Fr+
(2) +%28+r+%2B+.04+%29%2A%28+270%2Fr+%29+=+450+
(2) +270+%2B+10.8%2Fr+=+450+
(2) +10.8%2Fr+=+180+
(2) +180r+=+10.8+
(2) +r+=+.06+
and
+r+%2B+.04+=+.1+
The rate of interest for 1st CD is 6%
The rate of interest for 2nd CD is 10%
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check:
(1) +r%2AP+=+270+
(1) +P+=+270%2Fr+
(1) +P+=+270%2F.06+
(1) +P+=+4500+
and
(2) +%28+r+%2B+.04+%29%2AP+=+450+
(2) +%28+.06+%2B+.04+%29%2AP+=+450+
(2) +.1P+=+450+
(2) +P+=+4500+
OK