SOLUTION: Marissa invested $7000 for 1 year. Part was invested at 4% simple interest and part at 7% simple interest. At the end of 1 year, she had earned $391 in interest. How much had s

Question 731962:
Marissa invested $7000 for 1 year. Part was invested at 4% simple interest and part at 7% simple interest. At the end of 1 year, she had earned $391 in interest. How much had she invested at each rate?
Answer by checkley79(3341) (Show Source): You can put this solution on YOUR website!
.07X+.04(7000-X)=391
.07X+280-.04X=391
.03X=391-280
.03X=111
X=111/.03
X=$3,700 WAS INVESTED @ 7%
7000-3700=$3300 WAS INVESTED @ 4%
PROOF:
.07*3700+.04*3300=391
259+132=391
391=391
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