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GMAT Problem Dissection: Probability Part 2

July 25, 2013 by

Alright, you’ve been studying the GMAT basics. You understand what is really being tested along with the problem types, methods, and strategies. You’ve even memorized all the basic formulas and taken a dive into some of the more challenging content areas. So what’s next? That’s simple, practice…over and over and over again. If you do this, you are likely to start hitting tough probability questions at some point. Along with combinations and permutations, this is a content area that the GMAT can use to up the degree of difficulty quite a bit. So let’s take a look at a tough probability question and break it down:

A fair coin is tossed five times. What is the probability that it lands heads up at least twice?

(A) 1/16

(B) 5/16

(C) 2/5

(D) 13/16

(E) 27/32

The key to solving this is the phrase ‘at least twice.’ This means that … Read full post

GMAT Question Breakdown: Probability

June 11, 2013 by

iStock_000015742269SmallAll right, listen up. Here’s the deal. We know you guys are out there tearing it up and studying hard for the GMAT, so each week we’re going to break down a tough GMAT problem for you here on the blog. This will be straight to the point, outcomes-focused practice. No fluff. Let’s get down to business.

Question:

Each person in Room A is a student, and 1/6 of the students in Room A are seniors. Each person in Room B is a student, and 5/7 of the students in Room B are seniors. If 1 student is chosen at random from Room A and 1 student is chosen at random from Room B, what is the probability that exactly 1 of the students chosen is a senior?

(A) 5/42

(B) 37/84

(C) 9/14

(D) 16/21

(E) 37/42

Solution:

For those of you who love probability, you are rejoicing … Read full post

GMAT Quantitative Problems: Defining the Negative Space

August 20, 2012 by

GMAT blog, GMAT probability questions, GMAT combinations questions, GMAT quantitative sectionTake a look at the picture with this blog. It’s an iconic optical illusion. Stare at it—what do you see?  The picture is called the Great Wave off Kanagawa, painted by Katsushika Hokusai, a Japanese artist famed for his brilliant compositions. This drawing is of a wave, of course, but do you see the other wave, the reverse wave in the sky?

This image utilizes negative space. You take the whole frame, the great big rectangle, you block out that actual image—and what remains is, in its own right, an interesting picture.

You’ve seen this on the GMAT, of course. Images like this occur frequently on the Quantitative section:

GMAT blog, GMAT geometry problem

 

 

 

To find the area of the shaded region, we need to subtract the area of the smaller inner circle from the large outer circle—the difference is the area of the ring.

But the concept extends beyond … Read full post

Tough GMAT Probability Questions

August 16, 2012 by

GMAT blog, flipping a coin, probability of heads or tailsTackling some of the tougher GMAT probability questions efficiently relies on both steady practice and your ability to make two key decisions well. First, you will need to quickly and accurately assess the total number of possible outcomes (the denominator of your probability equation). Second, within a multitude of possible approaches, you will need to determine the most efficient route to calculate the number of desired outcomes (the numerator of your probability equation).

With the clock ticking away on your GMAT CAT, figuring out the total number of possibilities can be time-consuming and fraught with room for error. For instance, if a question asks about the probability of getting at least 2 heads on 5 coin tosses, you could sit there all day writing out possibilities:

HHTTT

HTHTT

HTTHT

So forth and so on. I know I got dizzy with the possibilities just writing those three out.  There is … Read full post

GMAT Quantitative Section: Probability Translation

August 8, 2012 by

GMAT blog, GMAT prep, GMAT quantitative section, GMAT practice problem, GMAT probabilityTranslating word problems into algebra is a staple skill of GMAT test-takers, one that underlies countless problems in practice and on Test Day. But some challenging translations occur as part of probability and combinatorics problems. That’s because a pair of the most basic words in the English language, “And” and “Or,” suddenly become overburdened with mathematical significance.

“And” is the simpler of the two. When “And” represents independent choices—cases in which one option or arrangement has no impact on the other choice—just multiply the outcomes. For instance:

“The number of ways to purchase three board games and two video games” is an independent choice. The board games we pick have no impact on the video games we pick. So, to translate: [The number of ways to purchase three board games] × [the number of ways to select two video games]. Of course, we’d need the combination … Read full post

Three GMAT Challenges

July 25, 2012 by

GMAT blog, GMAT study plan, GMAT goal, MBA applicationsPiecing together the time to study for the GMAT can be challenging.  In today’s blog, I’m going to talk about three students (whose names I’m changing to protect their identities).  Each had a major obstacle to studying, and each overcame it in a different way. I hope these students’ examples can help some of you reach your GMAT and MBA goals.

 

Case Study 1: Vincent, the Entrepreneur

The Challenge: Vincent was a busy man when I was tutoring him. His schedule was very flexible—his main source of income was a business that he started and ran himself—but he was distracted at all hours by emails and phone calls related to his work.

The Solution: Vincent needed a time and place where he could study in peace.

Because of his flexible work schedule, it was easier for Vincent to find time than it is for some other students. He … Read full post

2 Dice and the GMAT. What’s the relationship?

January 26, 2012 by

GMAT BlogWhile my students certainly accept that they have to take the GMAT, I often hear complaints about the applicability of GMAT topics – especially math – to real world situations.  My usual response to this observation is that the GMAT is using math questions to test critical thinking skills that business schools consider essential.

However, some GMAT problems have surprising real world applications outside the realm of business.  The sample problem below is an example of one such question.  Specifically, it can help you win at craps.

If you want to try the problem on your own, skip down to it now and then return here – part of this discussion will give you clues about the correct answer.

For those of you not familiar with craps, the basic play is fairly straightforward.  You roll two dice and if the sum of the result on each die is 7 … Read full post

 

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