Question 1156044
<br>
A traditional algebraic approach....<br>
x = amount at 2%
4000-x = amount at 7%
{{{.02(x)+.07(4000-x) = 230}}}<br>
Solve using basic algebra (straightforward, but it takes time)....<br>
Here is how I prefer to solve two-part "mixture" problems like this.  It uses only logical reasoning and a few simple mental calculations -- as opposed to writing and solving an algebraic equation.<br>
$4000 all at 2% would yield $80 interest
$4000 all at 7% would yield $280 interest
The actual interest of $230 is 3/4 of the way from $80 to $280 (80 to 280 is 200; 80 to 230 is 150; 150/200 = 3/4)
Therefore 3/4 of the $4000 was invested at the higher rate.<br>
ANSWER: 3/4 of the $4000, or $3000, was invested at 7%; the remaining $1000 was invested at 2%.<br>
CHECK:
.07(3000)+.02(1000) = 210+20 = 230<br>