SOLUTION: I invested $18,000. Part of it was invested at 3% annual simple interst and the rest was invested at 4%. I earned $650 in interest for the year. How much did I invest at each ra

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Question 160766: I invested $18,000. Part of it was invested at 3% annual simple interst and the rest was invested at 4%. I earned $650 in interest for the year. How much did I invest at each rate?
Answer by KnightOwlTutor(293) About Me  (Show Source):
You can put this solution on YOUR website!
Amount invested at 3%=x
Amount invested at 4%=18,000-x
Convert % into decimal format 3%=.03 4%=.04
The equation is as follows

.03x+.04(18,000-x)=$650

Use the distributive property
.03+720-.04x=650
Subtract 720 from both sides
add the two x terms
-.01x=-70
Divide both terms by -.01
x=$7000 invested at 3%
$18,000-$7,000=$11,000 invested at 4%
Let's double check our answer by calculating the interest generated by each portion and determining whether this amount equals the amount designated in the problem.

.03(7000)+.04(11000)=210+440=650
650=650