Question 1174081
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Here is a quick and easy non-algebraic alternative to the standard formal algebraic solution provided by the other tutor.<br>
The algebraic solution is of course fine.  But if obtaining a solution quickly is beneficial and a formal algebraic solution is not required (as in a timed math competition), this alternative method is very useful.<br>
All $28,000 invested at 6% would earn $1680 interest.
All invested at 4% would earn $1120 interest.
The actual interest was $1440.<br>
Determine, perhaps with the help of a number line, that the actual interest $1440 is $320/$560 = 32/56 = 16/28 of the way from $1120 to $1680.<br>
That means 16/28 of the total was invested at the higher rate.  (Note I left 16/28 in unsimplified form, because the total investment was $28,000.<br>
ANSWER: 16/28 of the $28,000, or $16,000, was invested at the higher 6% interest rate; the other $12,000 was invested at 4%.<br>
CHECK: .06(16000)+.04(12000) = 960+480 = 1440<br>