Question 1207481
.
<pre>

Let the 7% investment be x dollars;
 
then the 6% investment is (10000-x) dollars.


Partial interests from separate accounts are 0.07x and 0.06*(10000-x) dollars, respectively.


The total annual interest equation is

    0.07x + 0.06*(10000-x) = 660  dollars.


Simplify this equation and find x

    0.07x + 600 - 0.06x = 660

    0.07x - 0.06x = 660 - 600

        0.01x     =    60

            x     =    60/0.01 = 6000  dollars.


So, the 7% investment is $6000;  the 6% investment is the rest,  $10000 - $6000 = $4000.


        Thus you get the answer.


<U>CHECK</U>.  0.07*6000 + 0.06*4000 = 420 + 240 = 660  dollars.  ! precisely correct !
</pre>

Solved.


-----------------


The other person made an arithmetic error on the way and did not fix it.


This led him/her to wrong answer.



Let this example teaches you on how important is to make a full-size check at the end.


&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Without such full-size check the solution is not complete !


&nbsp;&nbsp;&nbsp;&nbsp;And can not be considered/recognized/accepted as an error-free !