Tracy invested 6000 dollars for 1 year, part at 10% annual interest and the balance at 13% annual interest. Her total interest for the year is 712.50 dollars. How much money did she invest at each rate?

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Answer 1 · 2015-11-07T16:36:16

$2250 @10%
$3750 @13%

Let #x# be the amount invested at 10%
#=> 6000 - x# is the amount invested at 13%

#0.10x + 0.13(6000 -x) = 712.50#

#=> 10x + 13(6000 -x) = 71250#

#=> 10x + 78000 - 13x = 71250#
#=> -3x + 78000 = 71250#

#=> 3x = 78000 - 71250#

#=> 3x = 6750#
#=> 2250#

#=> 6000 - x = 3750#