Question 1125428
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The algebraic solution method for this kind of problem is fine.<br>
But if you are working a lot of these problems, here is a method that will get you to the answer faster and with much less work.  (I am good at mental arithmetic; solving this problem takes me about 5 seconds by this method.)<br>
(1) The interest at 5% would be $80; the interest at 6% would be $96.
(2) Since $89 is 9/16 of the way from $80 to $96, 9/16 of the money should be invested at the higher rate.
(3) 9/16 of $1600 is $900.<br>
ANSWER: $900 at 6%; $700 at 5%.