HI RobertP,

What is the source of this question? I ask because it's poorly-written and you might be better served by studying with material that more closely follows the 'style' of the Official GMAT.

This prompt can be solved by TESTing THE ANSWERS, but there's a great pattern-matching 'shortcut' that you can take advantage of. Although the prompt does not state it, we're meant to assume that the money was invested for 1 year. IF half was invested at 10% and the other half was invested at 8%, then the interest for the two accounts would be....

$1,000 x 10% = $100
$1,000 x 8% = $80
Difference = 100 - 80 = $20
This difference is TOO SMALL (it's supposed to be $56). This means that MORE money had to be invested at 10%, so LESS THAN HALF was invested at 8%. Answers A and B are eliminated and you would just have to TEST Answer D.

If Answer D leads to a difference of $56, then you have the answer. If it's too high or too low, you'll know which 'direction' to go in and then you'll have the answer.

GMAT assassins aren't born, they're made,
Rich