SOLUTION: Robert invests $8000 in a bank. Part is invested at 7% simple interest and part at 9% simple interest. In one year Robert earns $660 in interest. How much did he invest at each amo
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Question 225520: Robert invests $8000 in a bank. Part is invested at 7% simple interest and part at 9% simple interest. In one year Robert earns $660 in interest. How much did he invest at each amount?
Answer by solver91311(24713) (Show Source): You can put this solution on YOUR website!
Let 
represent the amount invested at 7%. Then the amount invested at 9% must be 
. The amount of interest earned on the 7% investment is then 
and the amount earned on the 9% investment is )
. The sum of these two amounts earned is $660, so:
\ =\ 660)
Solve for to get the amount at 7% and subtract that amount from 8000 to get the other amount.
John
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