SOLUTION: Bob invested $21,000, part at 18% and part at 8%. If the total interest at the end of the year is $1,980, how much did he invest at 18%?

Question 106663: Bob invested $21,000, part at 18% and part at 8%. If the total interest at the end of the year is $1,980, how much did he invest at 18%?
Answer by elima(1433) (Show Source): You can put this solution on YOUR website!
Bob invested $21,000, part at 18% and part at 8%. If the total interest at the end of the year is $1,980, how much did he invest at 18%?
x+y=21000
.18x+.08y=1980
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x=21000-y
.18(21000-y)+.08y=1980
3780-.18y+.08y=1980
-.1y=-1800
y=18000
------------
x+18000=21000
x=3000
------------------
so he invested $3000 at 18%
:)
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