Posted on
20
Nov 2020

GMAT How-to: Probability Problems

GMAT probability questions, which test logical reasoning skills, tend to be quite daunting. The good news is that they don’t appear very frequently; the Quant section contains no more than three or four probability questions. However, since so many test-takers struggle with these questions, mastering probability can be an excellent way to boost your overall score. 

GMAT probability questions aren’t so hard once you’ve grasped the basic concepts. Like the majority of the Quant section, probability questions only cover high school level material. The principal challenge is the tricky wording. 

This article will cover some methods to simplify probability questions and boost your Quant score. 

What Is Probability?

The first step to mastering probability is to break down the basic idea:

Probability = the number of desired outcomes / the total number of outcomes

Or in other words, the chance of something happening is the quotient of the number of desired outcomes and the total number of possible outcomes.

A coin flip is one generic example that can help us understand probability.

There are two possible outcomes when we flip a coin: heads or tails. If we want the coin to land on heads, then we divide 1 (the chance that the coin will land on the desired outcome, heads) by 2 (all possible outcomes, heads and tails), and the result is ½ or 0.5 (50%), meaning that there is a 50% chance that the coin will land on heads.

Although this is an elementary example, it demonstrates the fundamental concept behind all probability problems–a ratio between a part and a whole expressed as a fraction or percentage.

Probability of Independent Events

The probability of x discrete events occurring is the product of all individual probabilities.

For example, imagine that we toss a coin twice. Each toss is independent of the other, meaning that each toss has an equal chance of landing on either heads or tails (0.5). If we want to calculate the chance of getting heads twice in a row, we need to multiply the probability of getting heads the first time by the probability of getting heads the second time. 

Or, represented as an equation:

 ½ x ½ = ¼ 

We get a 0.25 or 25% chance that the coin will land on heads twice. 

Probability of Getting Either A or B

Keep in mind that the sum of all possible events is equal to 1 (100%). 

If we continue with the coin toss example, we know that the probability of landing on heads is 0.5, and that the probability of landing on tails is also 0.5. Therefore:

0.5 + 0.5 = 1

The possibility of landing on either heads or tails is equal to 1, or 100%. In other words, every time we flip a coin, we can be certain that it will land on heads or tails.

Probability Of An Event Not Occurring

Following the concept that the sum of all possible events is 1, we can conclude that the probability of event A not happening (A’) is 1 – A, or equal to the probability of event B occurring.

The chance that the coin will not land on heads is equal to the chance that the coin will land on tails:

1 – 0.5 = 0.5

This method is most useful in situations with many favorable events and fewer unfavorable ones. Since time management is essential on the GMAT, it’s better to avoid solution paths that require more calculations. Subtracting the number of unfavorable events from the whole is quicker and simpler, and thus, less likely to result in mistakes.

Pay Attention to Keywords

Read each problem’s wording with great care to determine exactly which operations to use. 

For example, if the problem uses the word “and,” you need to find the product of the probabilities. If the question uses the word “or,” you need to solve for their sum.

If we flipped one coin and we wanted to know the chances of landing on either heads or tails, we would calculate it like this:

0.5 + 0.5 = 1

Similarly, if we were to toss two coins and we wanted to find the probability of landing on both heads and tails, we would use this equation:

0.5 x 0.5 = 0.25

Avoid Common Errors

Minor errors, such as missing possible events, can lead to incorrect answers.

These pointers will help you avoid some common mistakes on probability questions:

  • List all possible events before starting any calculations;
  • Sum up the probabilities of all possible events to make sure they add up to 1;
  • If there are several different arrangements possible (for example, picking different colored balls from a box), find the probability of one of the events and multiply it by the number of different possible arrangements.

If you enjoyed this article make sure to check out our other How To articles like: Efficient Learning & Verbal section.

 

Contributor: Altea Sulollari
Date: 20th November 2020

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Should You Retake the GMAT?
Posted on
14
Apr 2020

Should You Retake the GMAT? All That You Need to Consider

There it is. A 690. Not what you wanted, but pretty damn good. Should you keep the score or cancel it? Do you take the exam again, after all the agony, or hope that it will be enough?

GMAT test takers face these questions each time they sit the exam, and there is no one size fits all answer. There are many factors to consider, from your personal situation, available time, career and MBA goals, and the draw of being done with the GMAT.

1. You Are Not Your GMAT Score

Let’s begin with a more general premise: YOU ARE NOT YOUR GMAT SCORE. As much as some might have you believe so, your GMAT score is not the be all end all of your life, self-worth, or MBA candidacy. It’s important to keep this fact in mind, and what follows from it. While a strong GMAT score is necessary to demonstrate academic skill and preparedness for an MBA or other graduate program, a strong score is not enough, especially if you’re applying to a top-ranked program.

Something that almost no one will tell you – nearly everyone struggles on the GMAT and spends months preparing. We often see clients from top consulting and banking firms who insist on not recommending us to others because they don’t want anyone they work with to know that they needed help!

2. How The Admissions Committees View Your GMAT Score

An admissions committee is looking at your entire profile – your resume, recommendations, accomplishments, and presentation in an interview setting. While they use the GMAT to determine how well they believe you’ll thrive in the academic parts of the MBA program, they’re really looking at the individual when making a decision.

Admissions committees want to see you at your best, so having a second score on your score report, or even speaking about your struggles on the GMAT and how you overcame them can work as a positive to your application. Many programs are also willing to “super score” – taking the best subsections and combining them into the best possible score, and, especially on the quantitative, want to make sure that you’ll be able to handle the rigors of the program.

Having an inferior score on your score report is a lot like running a race slowly… No one cares about your worst time, they only care about your best. You might be tired, ill, have a nail in your shoe, or some other calamity, so only your best time represents your capability, and admissions committees know this. So when should you retake the GMAT? Well ask yourself the following question before you make that decision:

  • What Does This Increase Really Mean To You?

Another factor to consider is how much an incremental increase in your GMAT score will be compared with spending the time elsewhere – adding another activity to your resume, spending more time on crafting your essays, or even feeling better by going out and seeing friends more regularly so you don’t absolutely freaking lose it!

These are real considerations, and being well rounded in fact, not just on paper, will provide a notable enhancement to your ability to market yourself effectively and accomplish your goals – career, romantic, and otherwise. Are you really prepared to give so much up for a number on a piece of paper?

  • Why Should You Retake The GMAT?

On the other hand, perhaps you had an off day, or perhaps it is really important to you to crack that 700 because your brother/partner/boss got there and you want to be in that same rarefied air. There’s nothing wrong with that, and that drive can be a healthy one. Retaking the exam, especially after significant preparation, represents an extra $250 GMAT retake fee and an afternoon. Additional retakes are “free” relative to the time and commitment you’ve spent to get to the first exam, so to the extent, it’s not damaging to your mental health, relationships, and lifestyle, there’s absolutely no reason you shouldn’t take the exam one or more additional times. Admissions committees can’t see that you’ve canceled your scores, so don’t worry about looking try-hard. Besides, like everything in life, you’re doing it for you, right?

3. GMAT Retake Strategy

In the end, there is no right or wrong answer, just the answer that is right or wrong for you. Consult with your family, partner, friends, and colleagues. If you’re working with a professional GMAT tutor, they should be able to provide you perspective as well, especially since they’ve seen this many times before, and maybe have gone through it personally. If you would like to talk about your GMAT prep or retaking the GMAT with an Apex instructor leave us your details.

 

By: Mike Diamond, Director of Curriculum, Apex GMAT

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