Question 173357: Mr. Roberts invested $28,000, part at 18% and part at 9%. If the total interest at the end of the year is $3,240, how much did he invest at 18%??
Found 2 solutions by Mathtut, stanbon:
Answer by Mathtut(3670)   (Show Source):
You can put this solution on YOUR website! lets call the amount invested at 9%,x and the amount invested at 18, y
. we know that x+y=28000.....so y=2800-x
:
.09x+.18(28000-x)=3240
:
.09x+5040-.18x=3240
:
-.09x=-1800
:
$ amount invested at 9%
:
$ amount invested at 18%
Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website! Mr. Roberts invested $28,000, part at 18% and part at 9%. If the total interest at the end of the year is $3,240, how much did he invest at 18%??
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interest + interest = interest
0.18x + 0.09(28000-x) = 3240
18x + 9(28000-x) = 324000
9x = 324000- 9*28000
9x = 72000
x = 8000 (amt invested at 18%)
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Cheers,
Stan H.
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