Question 1142477
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Here is an alternative to the standard algebraic method for solving mixture problems like this, as shown by the other tutor.  If you understand how to use it, it will get you to the answer with much less effort than the algebraic method.<br>
(1) Determine the amounts of interest if the whole $15,000 were invested at each rate.
$15,000 at 3% = $450
$15,000 at 4% = $600<br>
(2) Picture the three interest amounts on a number line: 450, 520, and 600.<br>
(3) Use mental arithmetic or any method you want to determine that 520 is 7/15 of the way from 450 to 600.<br>
(4) That means 7/15 of the total was invested at the higher rate.<br>
ANSWER: 7/15 of $15,000, or $7000, at 4%; the other $8000 at 3%.<br>
CHECK: .04(7000)+.03(8000) = 280+240 = 520