Don’t 'Bury the Lead' on Data Sufficiency

Photograph by Larry Sultan/Gallery Stock

This tip for improving your GMAT score was provided by David Newland at Veritas Prep.

When a newspaper story does not mention the important parts until the end, and as a consequence these facts are overlooked by most readers, this is referred to as “burying the lead.” A better practice is to bring out the most important facts right away, so that readers will take note and read on.

On Data Sufficiency, “burying the lead” happens whenever a test taker fails to take notice of the facts contained in the question stem itself. When a test taker overlooks these facts, the chances of getting the question right diminish, and the chance of falling for a trap greatly increases.

Bring out the facts:

Try the following question taken from the Veritas Prep Data Sufficiency book. Focus on bringing out all of the facts.

If y is a positive odd integer, and the product of x and y = 222, what is the value of x?

1)  x is a prime number
2)  y is a 3-digit number

Do you have your answer? Let’s see how you did.

Begin with the actual question and take note of what you are attempting to answer. This is a specific number question that simply calls for one set value for x. If we can obtain just one value, that is sufficient.

From the question stem, we can derive several facts.

•  y is positive
•  y is integer
•  y is odd
•  xy = 222
•  and the deduction that x is even. (If x is an integer, that is. Notice that nowhere does it say x must be an integer, only y).

Carefully apply the facts to the statements:

Having done the work required to have a firm understanding of the question, we are ready to move to evaluate the statements.

Statement 1 indicates that “x is a prime.” This statement brings a couple of facts of its own. Saying “x is prime” means x must be an integer, and it must be a positive number. This is not something the question stem guaranteed.

If we combine what we learned from statement 1 with the “x is even” that we deduced from the question stem, then we are looking for the only even prime number. The only possible values are x = 2 and y = 111. Since this gives one single value for x, statement 1 is sufficient.

Statement 2 says that “y is a 3-digit number.” You now know that y is a positive, odd, 3-digit integer. All you know about x is that xy = 222.

The temptation here is to carry over some of the information from statement 1. If you think statement 2 requires x to be a positive integer, you are likely to judge statement 2 as sufficient. It is OK to use x = 2 and y = 111 as values for statement 2, but it is important that you not stop there; the common number properties “positive/negative” and “non-integers” should be investigated. Since Y is positive and xy = 222, x must also be positive. So for this question, negative numbers will not work.

Non-integers will still work with statement 2, however. Remember, the only reason you knew x has to be an integer in statement 1 was that statement 1 required x to be a prime number. All that statement 2 gives you is that y is a 3-digit number (and you know it is positive and odd). So y could be 999, and x could be 222/999. Multiplied together, x and y will still give a result of 222. Since x can be a number of different fractional values, statement 2 fails to give just one value and is not sufficient.

Bringing out the facts on data sufficiency is a key strategy. Taking note of what is written can help you also to see what is not written. Noting that y is an integer can lead you to think about x and the fact that x is not required to be an integer. This can help you avoid the trap in statement 2.

Don’t leave the most important information for last, or it might be overlooked. In other words, don’t “bury the lead” on data sufficiency.

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