Math Expert
Joined: 02 Sep 2009
Posts: 47918

GMAT Tip of The Week: Tonya Harding Teaches Data Sufficiency
[#permalink]
Show Tags
03 Dec 2014, 08:35
FROM Veritas Prep Blog: GMAT Tip of The Week: Tonya Harding Teaches Data Sufficiency

Twenty years later, the figure skater you’d never have called “trendy” was trending last night. As ESPN aired its 30 For 30 special on Tonya Harding and Nancy Kerrigan, the biggest preOJ story of 1994 became the hottest topic of early 2014. Heading into the 1994 Olympics, both Nancy and Tonya were Olympic veterans, having placed 3rd and 4th, respectively, at the 1992 Games. With 1992 gold medalist Kristi Yamaguchi out of the way, the table was set for a Nancy vs. Tonya showdown and both were up to the task, Tonya having been 1991 U.S. Champion and Nancy having won that title in 1993.
Tonya Harding was poised to recapture that glory of 199192, having shaken off some personal issues to refocus on skating. And with two Americans guaranteed to make the Olympic team, it seemed overwhelmingly likely that Nancy and Tonya would represent the U.S. together and that Tonya would have her bestever chance at an Olympic medal. And then it all came crumbling down because Jeff Gillooly doesn’t understand Data Sufficiency.
Here’s the question, and here are the facts. Will Tonya Harding make the Olympic team? The top two finishers make the team, and Tonya is as good as Nancy but maybe a little better or maybe a little worse, and both of them are better than the rest of the field. So if we assess this as a Data Sufficiency prompt, we’d have:
Is Tonya one of the two highest values in Set USA?
(1) Nancy > Tonya > all other values in Set USA
Statement 1 here is sufficient – if we can prove that Tonya is at the very worst the secondbest competitor, she’s guaranteed to make the team. But then along came Jeff Gillooly, not the sharpest tool in the shed, making one of the most common GMAT mistakes anyone can make.
Jeff Gillooly picked C.
Jeff Gillooly took a look at a Statement 2 that only existed in his own mind and went for it, hiring a goon to club Nancy Kerrigan in the knee and introduce this statement to the problem: “Set USA does not contain Nancy”. The problem then looked like:
Is Tonya one of the two highest values in Set USA?
(1) Nancy > Tonya > all other values in Set USA
(2) Set USA does not contain Nancy
Jeff Gillooly looked at that problem and made the same mistake that so many GMAT testtakers make. He thought “If together Nancy and Tonya are the two highest values, and then if Nancy isn’t in the set, then Tonya is guaranteed to be one of the two highest values in the set (and therefore make the Olympic team and win me and my creepball moustache a free trip to Norway!).” So Jeff Gillooly picked C, forgetting that there are two clauses to that answer choice:
(C) Both statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
Read past the comma, Gillooly. Tonya Harding was sufficient ALONE. With Nancy Kerrigan out of the picture, Tonya won the US Nationals meaning that even had Nancy been absolutely amazing on the ice in that competition Tonya at worst would have gotten second and gone to the Olympics. In GMATspeak, even though we all love having two pieces of information, if we only need one of them we’re punished for using both. If one statement alone is sufficient, you can’t pick C. Don’t be a Gillooly!
Since not many (if any) actual GMAT problems will be about Tonya Harding, let’s see this same concept in action with a real GMAT problem:
Is 0 < x < 1?
(1) x^2 < x (2) x > 0
As you unpack statement 1, you’ll probably recognize that a fraction like 1/2 satisfies that inequality. If you square 1/2 you get 1/4, a number less than the original. So most people will look at statement 1 and say “x has to be a fraction, so that’s probably sufficient”. But then statement 2 hits a lot of people’s minds like a club to the knee – “Oh, but I need to know that it’s positive, too! I’ll pick C.”
Go back, though – if you try a negative fraction like 1/2, when you square it it becomes positive, and x^2 is greater than x. Statement 2 already tells us that x is positive – statement 1 is sufficient ALONE. All statement 2 really does is reinforce something that was already sufficient alone. Statement 2 is the Gillooly trap. Before you pick C, you’d better make sure that neither statement is sufficient ALONE. And like in the Nancy/Tonya situation, a statement (or skater) is often sufficient ALONE only through some hard work – beware the “easy way out” statement that makes C seem “obvious” when you could have taken a few extra steps (a little extra algebra, some extra work on your triple salchow) to make a statement sufficient ALONE.
There are plenty of lessons that a GMAT testtaker can take from the Nancy/Tonya saga – cheaters always get caught, make sure your shoelaces are tied before you enter the test center – but one reigns supreme above them:
Don’t use both statements if one alone will do the trick. Don’t be a Gillooly.
Are you studying for the GMAT? We have free online GMAT seminars running all the time. And, be sure to find us on Facebook and Google+, and follow us on Twitter!
By Brian Galvin

ForumBlogs  GMAT Club’s latest feature blends timely Blog entries with forum discussions. Now GMAT Club Forums incorporate all relevant information from Student, Admissions blogs, Twitter, and other sources in one place. You no longer have to check and follow dozens of blogs, just subscribe to the relevant topics and forums on GMAT club or follow the posters and you will get email notifications when something new is posted. Add your blog to the list! and be featured to over 300,000 unique monthly visitors
_________________
New to the Math Forum? Please read this: Ultimate GMAT Quantitative Megathread  All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
Collection of Questions: PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.
What are GMAT Club Tests? Extrahard Quant Tests with Brilliant Analytics
