Data Sufficiency

Q. Does abcd = 1?

(1) abc = 1
(2) bcd = 1

Without doing any 'work', explain why must the answer be TOGETHER NOT sufficient?

Solution:

[spoiler]The question asks whether the product of four variables will be 1. The variables are completely unqualified, so to answer this question something must be known about each variable.

Statement (1) provides a relationship between three of the variables so it is insufficient.

Statement (2) provides a relationship between three of the variables so it is insufficient.

This eliminates three answers choices.

Taken together the Statements do provide information about all four variables, but is that information enough? Let's use the Schrute test.

Dwight Schrute once said, "Whenever I'm about to do something, I think, "Would an idiot do that?" And if they would, I do not do that thing."

Let's modify this for the GMAT: "Whenever I'm about to pick an answer, I think, "Would a typical GMAT taker pick that answer?"And if they would, I do not pick that answer."

Would a typical GMAT taker think that Statements (1) and (2) were sufficient? Yes, he would. Therefore we must pick TOGETHER NOT sufficient.[/spoiler]

This strategy is not intended to replace doing the 'work.' But it can bolster confidence and prevent GMAT takers from falling into the common trap of complementary-looking Statements.