Friday, September 14, 2012

GRE Tips and Tricks!: Quantitative: Quantitative Comparisons


Let's start with the basics of the Quantitative Section: you have thirty five minutes to answer twenty questions. There are four types of questions: Quantitative Comparison, Multiple Choice with one correct answer, Multiple Choice with more than one correct answer, and Numeric Entry. I will be walking you through each question type. Math isn't your forte? That's fine, we'll help you get prepared enough that when the time comes you'll be doing problems like its old hat. I would also like to mention that should you have any questions to feel free to post your question in the comments below and either Serena or I will get to it as soon as we can.

Ready? Take a deep breath, its go time. 


Quantitative Comparisons 


Quantitative comparisons are exactly what they sound like: comparisons using numbers. You are given two mathematical expressions in two columns, A and B. Your job is to compare them and you may be given additional information to help you with this. There are FOUR answer choices and they NEVER CHANGE therefore if will save you a bit of time memorizing them now so don't have to keep rereading them on test day.

The four answer choices are as follows:
A. quantity in Column A is greater
B. quantity in Column B is greater
C. the two quantities are equal
D. the relationship cannot be determined from the info given.

Not only do these answers not change but answer D can give you a hint to your answer. If both columns only have numbers (so no variables) that means that their relationship will not change in which case D will NEVER be correct. If you can show that there is more than one CORRECT relationship between the two columns then D will always be correct. Got it so far? So only numbers, can't be D. More than one answer, can only be D. 

So how do we go about answering these types of questions? I've put together a few tips that will help you answer the question quickly.

Tip 1: Estimate where you can
Often you can do not need to calculate an exact value. Estimate your values and solve from there, it will save you time and often eliminate most or all of the wrong answers. 

Tip 2: Make Column A like Column B
Yes I do realize that's a vague title. What I mean is that if column A is in fractions and B in decimals convert them both to fractions. This will make your math much easier. Same goes for percents and parentheses.

Tip 3: Treat the two columns as an inequality
Treat the two columns as two sides of an inequality and apply math to them to simplify them. For example if Column A says 3x+4 and Column B says 4x+4 subtract 4 from both sides to simplify. This can also help you get rid of fractions/decimals. NOTE: Remember we are treating this as an inequality so do not multiply or divide by a negative number unless you are SURE beyond doubt that both columns are positive. 

Tip 4: Pick Numbers
Easiest trick in the book. Can't figure it out? Pick random numbers (be careful that if given additional information the number you pick qualify) and plug them into the question to solve. Here's the catch, you have to do it AT LEAST TWICE. This is key. Say you plugged in only positive whole numbers the first time but when you use a negative your answer becomes false, you would have missed it if you hadn't checked again. So always for your second Set choose a negative, or an extremely large or small number, or a fraction, etc. The variables can be positive, negative, zero, or fractions.  I'm not saying pick the hardest numbers you can think of; on the contrary I'd suggest you pick easy numbers. Just make sure to be diverse with your choices.

Tip 5: Redo all diagrams if necessary
Unlike the SAT, diagrams on the GRE are NOT DRAWN TO SCALE. What may look like a ninety degree angle may not be one. If the diagram given confuses you in the least then just redraw the diagram to exaggerate the differences so that you have no chance of mistaking angles/sides/etc from one another. 



That's all for today but stay tuned for my next post!

Cheers,

N. Riazi

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