SOLUTION: kristen has a total of $1000 to invest. she put parts of it in an account paying 4% interest/year and the rest in bond paying 6.5% interest. if she has $50 in simple interest at th

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Question 1068523: kristen has a total of $1000 to invest. she put parts of it in an account paying 4% interest/year and the rest in bond paying 6.5% interest. if she has $50 in simple interest at the end of the year, how much was invested at each rate?
Found 2 solutions by Fombitz, josmiceli:
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
1.A%2BB=1000
2.4A%2B6.5B=5000
Multiply eq. 1 by 4 and subtract from eq. 2,
4A%2B6.5B-4A-5B=5000-4000
2.5B=1000
Now solve for B.
Then use either equation to solve for A.

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
This looks like a simple interest problem
I can use:
+I+=+P%2Ar%2At+ where
+I+ = interest after +t+ years
+P+ = amount invested
+r+ = interest rate
+t+ = years invested
------------------------------------------------
+I%5B1%5D+=+P%5B1%5D%2Ar%5B1%5D%2At+
(1) +I%5B1%5D+=+P%5B1%5D%2A.04%2A1+
(1) +P%5B1%5D+=+25I%5B1%5D+
and
+I%5B2%5D+=+P%5B2%5D%2Ar%5B2%5D%2At+
(2) +50+-+I%5B1%5D+=+%28+1000+-+P%5B1%5D+%29%2A.065%2A1+
-------------------------------------------
(2) +50+-+I%5B1%5D+=+65+-+.065P%5B1%5D+
(2) +I%5B1%5D+=+.065P%5B1%5D+-+15+
Substitute (1) into (2)
(2) +I%5B1%5D+=+.065%2A25%2AI%5B1%5D+-+15+
(2) +I%5B1%5D+=+1.625I%5B1%5D+-+15+
(2) +.625I%5B1%5D+=+15+
(2) +I%5B1%5D+=+24+
and
(2) +I%5B2%5D+=+50+-+I%5B1%5D+
(2) +I%5B2%5D+=+50+-+24+
(2) +I%5B2%5D+=+26+
-----------------------
(1) +P%5B1%5D+=+25I%5B1%5D+
(1) +P%5B1%5D+=+25%2A24+
(1) +P%5B1%5D+=+600+
and
+I%5B2%5D+=+P%5B2%5D%2A.065%2A1+
+26+=+P%5B2%5D%2A.065+
+P%5B2%5D+=+26%2F.065+
+P%5B2%5D+=+400+
-----------------------
$600 was invested @ 4%
$400 was invested @ 6.5%
------------------------
check:
+P%5B1%5D+%2B+P%5B2%5D+=+1000+
+600+%2B+400+=+1000+
and
+I%5B1%5D+%2B+I%5B2%5D+=+50+
+24+%2B+26+=+50+
OK