Hi AbeNeedsAnswers,
We're told that A, B, C, and D are points on a line, C is the midpoint of line segment AB and D is the midpoint of line segment CB. We're asked if the length of line segment DB is greater than 5. This is a YES/NO question.
You might find it useful to draw a picture (and it would likely help you to make the algebraic 'deductions' that are needed to answer this question).
< - - A - - - - - C - - D - - B - - >
In the above example, C is the midpoint of AB and D is the midpoint of CB, so...
AC = CB = X
CD = DB = Y
X = 2Y
The question essentially asks if Y is greater than 5.
1) The length of line segment AC is greater than 8
With Fact 1, we know that X is greater than 8. This means that Y is greater than 4.
IF... Y = 6, then the answer to the question is YES.
IF... Y = 5, then the answer to the question is NO.
Fact 1 is INSUFFICIENT
2) The length of line segment CD is greater than 6
With Fact 2, we know that Y is greater than 6. Thus, the answer to the question is ALWAYS YES.
Fact 2 is SUFFICIENT
Final Answer: B
GMAT assassins aren't born, they're made,
Rich
