Hi amitmj,
You're correct that this DS question is essentially about algebra....
We're told that apples weigh 6.5 ounces each and pineapples weigh 13 ounces each. We're also told that a vendor sells twice as many apples as pineapples. This translates into....
A = number of apples
P = number of pineapples
A = 2P
We're asked for the value of A.
Fact 1: She sells 8 more apples than pineapples.
This translates into....
A = P + 8
Combined with the information from the prompt (A = 2P), we now have a "system" of equations (2 variables and 2 unique equations). This means that we CAN solve for A and P (and answer the question. The best part is that we don't have to do the math.
Fact 1 is SUFFICIENT
Fact 2: The vendor sells an equal amount, by weight, of apples and pineapples.
This translates into....
6.5A = 13P
This simplifies to...
A = 2P
Unfortunately, this information is REDUNDANT to the information we were given in the prompt. The information in Fact 2 means that the vendor sold twice as many apples as pineapples. We already knew that. So Fact 2 does NOT give us anything new to work with. We still cannot answer the question.
Fact 2 is INSUFFICIENT.
Final Answer: A
GMAT assassins aren't born, they're made,
Rich