Here’s a fairly straightforward GMATPrep question that I’ve seen manyastudent answer incorrectly. See if you can answer the question without writing anything down:
Of the 3,600 employees of Company X, 1/3 are clerical. If the clerical staff were to be reduced by 1/3, what percent of the total number of the remaining employees would then be clerical?
A) 25%
B) 22.2%
C) 20%
D) 12.5%
E) 11.1%
Classic GMAT question. Straightforward. Easy to understand. Simple to equate” 1/3 of 3,600 is 1,200 and 1/3 of that is 400. So we’d only have 800 remaining clerical staff and 800/3600 = 2/9, answer B. And like so(oooooooo) many other GMAT questions, we’d have answered incorrectly.
If have some paper in front of you, try to solve the question again by writing down each step along the way. Maybe even include what each of those numbers that you write down mean in the context of the question. Don’t cheat see if you answer the question differently when you’re forced to write down more than just a simple computation or two.
…
Here’s what I wrote down first on my scrap paper:
Clerical 
Other 
Total 

Before  
After 
Nothing magical here and it does require me to fill out a lot more than I might otherwise have written down, but when I fill in ALL of the information it becomes clear what I did wrong.
Clerical 
Other 
Total 

Before 
1200 
2400 
3600 
After 
800 
2400 
3200 
800 out of the remaining 3,200 employees is 1/4 or 25%. Answer A is correct.
They say that people can only remember four things at a time. Which is why it’s not surprising that a question like this requires just a few more than four numbers in order to solve. Few enough to think that you can solve the question without using paper. More than enough to guarantee that some people don’t.
Write down the thoughts of the moment. Those that come unsought for are commonly the most valuable.
~ Francis Bacon
The above example definitely isn’t a 700+ level question and many students get this question correct. But the ones who do answer incorrectly are usually doing so because they think that the couple of seconds that they save by not writing down a few words (or even letters I’ve done enough of these problems to remember that B & A stand for before and after), an equation, or some other easytoremember piece of the puzzle, will be the seconds that they need to finish the GMAT. Instead, the seconds that they save are spent deciphering what all those numbers on the page mean.
Students sometimes ask whether they should use a grid to solve a question or use some different method. But this isn’t a true dichotomy. Grids don’t solve questions, but they do help you with changing values B & A, with categorizing overlapping groups, or with adding rates in work problems. Learn the strategies associated with each question type to actually solve each question, but using a grid will help you to keep track of which numbers you will be using.
Here’s just a few of the things that I still write down when I’m doing GMAT problems. Feel free to add more in the comments!
1) Geometry Figures including points, angles, sides, and anything else they tell me
2) Unique Equations writing the equation and then plugging the numbers below allows me to use my full concentration on each step rather than using half my concentration trying to do both things at once
3) Memorized Equations I know that distance = rate Ã— time, but seeing it on my paper reminds me where each piece of information should go
4) Long Calculations writing the whole calculation out sometimes helps me see where I can save time (i.e. 2 Ã— 1/2 = 1 or 2 Ã— 5 = 10; both easier numbers to work with)
5) Sequences especially when trying to recognize patterns that may emerge and make less calculation possible
6) Critical Reasoning Conclusions when I have difficulty with a CR question, I concentrate on trying to solve one piece at a time, usually starting with a very abbreviated version of the main conclusion
* GMATPrep questions courtesy of the Graduate Management Admissions Council. Usage of this question does not imply endorsement by GMAC.
Well explained Joe. Point noted
Its often necessary for me to illustrate things just a bit.