November 22, 2018 November 22, 2018 10:00 PM PST 11:00 PM PST Mark your calendars  All GMAT Club Tests are free and open November 22nd to celebrate Thanksgiving Day! Access will be available from 0:01 AM to 11:59 PM, Pacific Time (USA) November 24, 2018 November 24, 2018 07:00 AM PST 09:00 AM PST Attend this webinar to learn how to leverage Meaning and Logic to solve the most challenging Sentence Correction Questions.
Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 50730

How to Solve Simple Math Equations on the GMAT
[#permalink]
Show Tags
22 Apr 2015, 03:12
FROM Veritas Prep Blog: How to Solve Simple Math Equations on the GMAT

Many students who take the GMAT come from backgrounds that stressed mathematics. A significant percentage of GMAT test takers come from engineering backgrounds or other fields that require strong analytical skills. However, these students often find that the GMAT quantitative section is challenging for them. This is because the GMAT tests math in a way that is unfamiliar to these students, taking them out of their comfort zones and requiring them to solve questions in new and unfamiliar ways (most glaringly, without a calculator).
Students who were never very fond of math in high school (and even kindergarten) often struggle with the math on the GMAT, but this is somewhat expected. If you never liked a topic, you probably never spent hours thinking about it or doing exercises in your leisure time (think of people who dislike cardio). However, many students who traditionally excel at math struggle just as much as the students who never cared for the subject. This frustration can be even more pronounced when it’s about a topic you’ve traditionally excelled at over your life.
Delving into the topic a little, the GMAT does not allow you to have a calculator with you during the exam because the calculator is a crutch that will end up doing the work for you. Naturally, in every conceivable real world situation, you will have a calculator with you, but finding ways to get the correct answer is an important aspect of business. When a decision needs to be made in a split second, you cannot always reach for your calculator. Worse than that, a calculator is clearly faster and more accurate than you, but we cannot (yet) be replaced by computers because computers cannot think as humans do (#Skynet). If the goal of the GMAT was to ensure that all students could perform complex mathematical calculations, you’d have a TI graphing calculator attached to your arm. The goal of the exam is to make you think, and nothing mitigates independent thinking like a calculator.
So how does the exam test math if it won’t give you complex math? Basically by giving you simple math and expecting you to solve it quickly. Simple math does not necessarily mean small numbers. In fact, large, unwieldy numbers are a great way to validate that you understand the underlying concept rather than utilize a brute force approach to solve the problem.
Let’s look at a very simple math question that helps to underline the kind of math problems you should be able to execute quickly:
What is 1,800 / 2.25?
(A) 400
(B) 500
(C) 650
(D) 800
(E) 850
On the actual GMAT, you might only see this question if you’re scoring in the bottom quintile of the test. However, you can easily have a calculation such as this to execute as part of a larger problem. Either way, getting the correct answer on a question such as this should ideally take you 30 seconds or less.
There are many ways to get the correct answer here, and the method chosen has a lot to do with personal preference. As someone who is comfortable with mental math, I would immediately attempt to approximate this equation. If it were simply 1,800 / 2, the answer would be 900. Since 2.25 is bigger than 2, the answer must be a little smaller. This narrows the choice down to likely either D or E. Rounding 2.25 to 3 would yield a division with a quotient of 3, further cementing the elimination of answer choices A and B. However between 800 and 850, the choice is pretty close, so we might need a more precise approach.
One common strategy is to convert the decimal into a fraction. Using algebraic rules, this might simplify our math quite a bit. 1,800 / 2.25 is the same as 1,800 / (9/4). This equation might seem equally daunting, but remember that division is the same thing as multiplication, and dividing by 9/4 is the same as multiplying by 4/9 (this property holds for all numerators and denominators). If I turned this into 1,800 * 4/9, I can think of it as two separate steps: (1,800 * 4) / 9, or (1,800 / 9) * 4 (commutative property). The second is clearly much easier to process, and you end up with 200 * 4, or 800. The answer must thus be D and can be seen fairly cleanly using fractions.
You can also get the answer by using reverseengineering. Simply put, an equation of 2.25 * x = 1,800 would yield the same x, so you can think of this equation as backwards. If x were 1, the product would be 2.25, which is clearly not the right answer. How can I get closer to the actual product? Well if I set x to be 4, then the product would be 9. From 9, I might be able to see that I could set x to be 40 and then 400, giving 90 and 900 respectively. Once I’m at 900, I simply double x (from 400 to 800) and get the correct answer. This strategy can be helpful for those who dislike division and prefer to work with multiplication.
Overall, it doesn’t matter which strategy you use (in fact you may use an entirely different approach and still get the correct answer. There is no “correct” strategy on the GMAT, only the Machiavellian notion that you must get the correct answer, by algebra, deduction, induction, strategic guessing or even dumb luck. Being able to solve math questions in roughly as long as it would take to solve if you had a calculator will help you realize why the tool is not allowed on the exam. In the best case, you can turn math on its ear and appreciate the nuanced way the GMAT tests your understanding of these fundamental concepts.
Plan on taking the GMAT soon? We have GMAT prep courses starting all the time. And, be sure to find us on Facebook and Google+, and follow us on Twitter!
Ron Awad is a GMAT instructor for Veritas Prep based in Montreal, bringing you weekly advice for success on your exam. After graduating from McGill and receiving his MBA from Concordia, Ron started teaching GMAT prep and his Veritas Prep students have given him rave reviews ever since.

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



NonHuman User
Joined: 09 Sep 2013
Posts: 8869

Re: How to Solve Simple Math Equations on the GMAT
[#permalink]
Show Tags
27 Aug 2018, 22:25
Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up  doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Books  GMAT Club Tests  Best Prices on GMAT Courses  GMAT Mobile App  Math Resources  Verbal Resources




Re: How to Solve Simple Math Equations on the GMAT &nbs
[#permalink]
27 Aug 2018, 22:25






