GMAT Probability Problems
Posted on
12
Aug 2021

GMAT Probability Problems – How to Tackle Them & What Mistakes to Avoid

By: Apex GMAT
Contributor: Ilia Dobrev
Date: August 12, 2021

The concept of probability questions is often pretty straightforward to understand, but when it comes to its application in the GMAT test it may trip even the strongest mathematicians.

Naturally, the place to find such types of problems is the Quantitative section of the exam, which is regarded as the best predictor of academic and career success by many of the most prestigious business schools out there – Stanford, Wharton, Harvard, Yale, INSEAD, Kellogg, and more. The simple concept of probability problems can be a rather challenging one because such questions appear more frequently as high-difficulty questions instead of low- or even medium-difficulty questions. This is why this article is designed to help test-takers who are pursuing a competitive GMAT score tackle the hazardous pitfalls that GMAT probability problems often create.

GMAT Probability – Fundamental Rules & Formulas

It is not a secret that the Quantitative section of the GMAT test requires you to know just the basic, high-school-level probability rules to carry out each operation of the practical solution path. The main prerequisite for success is mastering the Probability formula:
Probability = number of desired outcomes / total number of possible outcomes

Probability = number of desired outcomes
total number of possible outcomes

We can take one fair coin to demonstrate a simple example. Imagine you would like to find the probability of getting a tail. Flipping the coin can get you two possible comes – a tail or a head. However, you desire a specific result – getting only a tail – which can happen only one time. Therefore, the probability of getting a tail is the number of desired outcomes divided by the number of total possible outcomes, which is ½. Developing a good sense of the fundamental logic of how probability works is central to managing more events occurring in a more complex context.

Alternatively, as all probabilities add up to 1, the probability of an event not happening is 1 minus the probability of this event occurring. For example, 1 – ½ equals the chance of not flipping a tail.

Dependent  Events vs. Independent Events

On the GMAT exam, you will often be asked to find the probability of several events that happen either simultaneously or at different points in time. A distinction you must take under consideration is exactly what type of event you are exploring.

Dependent events or, in other words, disjoint events, are two or more events with a probability of simultaneous occurrence equalling zero. That is, it is absolutely impossible to have them both happen at the same time. The events of flipping either a tail or a head out of one single fair coin are disjoint.

If you are asked to find a common probability of two or more disjoint events, then you should consider the following formula:

Probability P of events A and B   =    (Probability of A) + (Probability of B)

Therefore, the probability of flipping one coin twice and getting two tails is ½ + ½.

If events A and B are not disjointed, meaning that the desired result can be in a combination between A and B, then we have to subtract the intersect part between the events in order to not count it twice:

Probability P of events A and B   =    P(A) + P(B) – Probability (A and B)

Independent events or discrete events are two or more events that do not have any effect on each other. In other words, knowing about the outcome of one event gives absolutely no information about how the other event will turn out. For example, if you roll not one but two coins, then the outcome of each event is independent of the other one. The formula, in this case, is the following:

Probability P of events A and B   =    (Probability of A) x (Probability of B)
How to approach GMAT probability problems

In the GMAT quantitative section, you will see probability incorporated into data sufficiency questions and even problems that do not have any numbers in their context. This can make it challenging for the test taker to determine what type of events he or she is presented with.
One trick you can use to approach such GMAT problems is to search for “buzzwords” that will signal out this valuable information.

  • OR | If the question uses the word “or” to distinguish between the probabilities of two events, then they are dependent – meaning that they cannot happen independently of one another. In this scenario, you will need to find the sum of the two (or more) probabilities.
  • AND | If the question uses the word “and” to distinguish between the probabilities of two events, then they are independent – meaning their occurrences have no influence on one another. In this case, you need to multiply the probabilities of the individual events to find the answer.

Additionally, you can draw visual representations of the events to help you determine if you should include or exclude the intersect. This is especially useful in GMAT questions asking about greatest probability and minimum probability.

If you experience difficulties while prepping, keep in mind that Apex’s GMAT instructors have not only mastered all probability and quantitative concepts, but also have vast experience tutoring clients from all over the world to 700+ scores on the exam. Private GMAT tutoring and tailored customized GMAT curriculum are ideal for gaining more test confidence and understanding the underlying purpose of each question, which might be the bridge between your future GMAT score and your desired business school admissions.

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Posted on
13
Oct 2020

The Online GMAT Experience-from preparation to post MBA 

Advancements in technology, combined with constraints caused by the COVID-19 pandemic, have prompted the GMAT world to adapt by shifting a large portion of the exam and preparation materials online. Both test takers and tutoring firms have seen positive outcomes from interactive learning aids, an abundance of resources, and easily accessible networks of people at different stages of the GMAT journey. However, the transition has also introduced some hazards concerning physical test endurance, focus, and anxiety. This article evaluates risks and challenges you may encounter taking the online exam and summarizes everything you need to know to be ready for your online GMAT experience.

The Online GMAT Exam

Since the onset of the pandemic in the spring of 2020, the General Management Admissions Council (GMAC) has introduced an innovative, completely online version of the physical GMAT test. This allows test takers to maintain social distance by sitting for the exam from the comfort of home.

As of late July, 2020, at the time of writing, anyone can schedule an online exam before December 31, 2020. In order to accommodate candidates’ availability, appointments are available 24 hours a day, 7 days a week, 24 hours before an available time slot. Note that the online GMAT exam is not available in Mainland China, Cuba, Iran, North Korea, and Sudan due to local data privacy regulations.

Differences From the Regular GMAT Exam

  • The GMAC has determined that the Quantitative, Verbal, and Integrated Reasoning sections are the most relevant for graduate business education. Therefore, the Analytical Writing Assessment (AWA) has been excluded from the online GMAT test.
  • The duration of the online test is shorter–2 hours and 45 minutes compared to 3 hours and 23 minutes. This time frame includes a 15 to 30 minutes tutorial to  familiarize candidates with the online proctored platform and all its functions.
  • Online, you will not be able to choose the order of the sections. The sequence is fixed as follows: Quantitative, Verbal, and Integrated Reasoning.
  • You can use a physical whiteboard, the built-in online whiteboard, or both for note taking. 

If you’re planning to use a physical white board, there are several requirements it must fulfil: it should be no larger than 12×20 inches (30×50 centimeters), use up to 2 dry erase markers and 1 dry erase whiteboard eraser. Items such as whiteboards with grids, background colors, or other markings, paper, pen, pencil, permanent marker, tissues (paper towels, napkins), whiteboard spray, chalkboards, writing tablets, and others are not permitted.

During the online exam, test takers will be able to access an online board from the icon. It contains an endless canvas to take notes on, which eliminates the need to erase your work as you progress through the sections.

  • In contrast to the two optional breaks in the regular exam, the online GMAT allows candidates to opt for only one 5-minute break before the Integrated Reasoning section.
  • Official GMAT scores are available on mba.com within 7 business days of completing the exam.
  • Another perk of the online GMAT experience is that it allows applicants to send scores to an unlimited number of institutions free of charge.
  • The online GMAT fee is $200, compared to the original $250 cost for the physical exam.
  • The online test cannot be retaken for any reason except a verified technical issue or authorized retakes.

Similarities With the Regular GMAT Exam

  • The online GMAT consists of the same Quantitative, Verbal, and Integrated Reasoning sections. Despite excluding the Analytical Writing Assessment (AWA), each of the other three sections contains the same number of questions as before–31, 36, and 12 respectively. In terms of timing, there are no alterations–the sections take 62, 65, and 30 minutes.

online GMAT breakdown

  • To ensure that GMAT scores are compatible and comparable across the online and test center-based versions, the online version adopts the same scoring algorithm. This means that both exams are equally replaceable with one another. 
  • Validity remains the same – 5 years.

Online GMAT Preparation, Tips & Tricks

As the online exam practically covers the same content, regular GMAT preparation remains relevant. If you are trying to figure out which prep method (self, group, or one-on-one) suits you best, you can check out the Four Ps of the best GMAT Prep. Apex’s GMAT tutors and custom-made curriculum are tailored to meet the needs for an online learning environment by providing private GMAT tutoring and nurturing constant feedback.

From a technical viewpoint, it is important to get used to the online whiteboard tool. It is available in all of GMAC’s Official Practice Exams, where anyone can practice all its functions in a simulated, timed environment. Keep in mind that you are not permitted to use touchscreens, graphics tablets, or stylus pens. And lastly, before starting the online GMAT exam, you can do a system test before to ensure your computer meets the operational requirements.

Contributor: Ilia Dobrev
Date: 13th October, 2020

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