GMAT Probability Questions

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Probability Questions

If Atima studied for eight hours a day for 20 days for GMAT, what is the probability that she’d end up getting a good GMAT score? You won’t find a question exactly like that in your GMAT exam. Most students get confused with the probability questions in the quantitative section, if you are one of them, don’t worry. Here is all the information that you will need about probability questions for GMAT which can help you prepare better. 

Where is Probability Used? 

Unlike a variety of topics from a maths book that might not be applicable in our routine life, the probability is a topic that is used every now and then. It is all about making speculations for calculating the chances of happening a particular event. It is one of the most interesting topics that you will get to study during your educational journey but it does not suffice till there. You would have definitely come across a plethora of situations where you make assumptions about the happening of a particular task. Apart from the everyday usage of probability, you will find this topic in the maths syllabus class 7 onwards. Along with this, it is also evidently seen in the syllabus of competitive exams like GMAT, GRE, CAT, SSC etc.

Also Read: Probability Formulas and Concept

Things to Keep in Mind While Solving Probability Questions 

Before getting started on how to solve probability questions, here are some essential things you should keep in mind while solving probability questions. The probability questions come in the quantitative section of the GMAT question paper to test your mathematical concepts. Here are some tips to understand probability questions better:

  • Probability is the result of dividing the number of desired digits to the number of possible results. Probability is basically figuring out the chances of getting the desired number. You can figure out the probability of a situation such as expecting a heads while flipping a coin by dividing the number of desired digits to the number of possible results. The only two outcomes are heads and tails. So, the probability of getting heads is ½. Probability questions on the GMAT are not going to be this easy but this is a simple way of understanding it better.
  • The probability of getting a certain result is the sum of two probabilities.The probability of getting one result or another means that you are looking for a single situation to happen. So, if you’re looking to find the probability of flipping a coin for getting heads or tails you have to find the probability of both. The probability of flipping a coin and getting the desired outcome is 50%. The probability of flipping a coin and not getting the desired outcome is also 50% so the probability of flipping a coin and getting heads or tails is ½ +½ =1.You should keep this point in mind while solving probability questions on the GMAT.
  • The probability of getting two different results is the outcome of two different probability analysis. Finding two different probabilities with a similar pattern is only possible after finding the probability of two situations individually. For example, if you flip a coin twice, each time the coin will flip differently at its own pace. That way they won’t affect each other. So for finding the probability for two different results you have to find the individual probabilities. 
  • The probability of something not happening is one minus the probability of the outcome.For finding the probability of something which won’t happen, you need to find the probability of something that will happen. If you’re trying to find the probability of flipping a coin and not getting heads, first try finding the probability of flipping a coin and getting tails. The probability of getting heads is 50 %. You have to minus the result by 1 so that the probability of getting the desired outcome becomes 50%. 

Probability Questions for GMAT: Solved Examples

There is a printing press that has two handles on the left and right sides. Each of the handles either works or breaks. Also, the working or non-working of each of the handles is independent of the failure or non-failure of the other. You can still use the machine with one handle. ⅗ is the probability that the left handle works and ⅗ is also the probability that the right handles works. What is the probability that you can still use the machine? 

Solution:
Let us begin by analyzing the probability of what we can’t do with the machine- 
 It will be, 
2/5 x 2/5 = 4/25 
You must be familiar with the formula: 
1- P’= P 
(P’= Probability of Not, P= Probability) 

According to the formula- 
1- 4/25= P 
(25-4)/ 25= P 
21/25= P 

The probability  that we can still use the machine is 21/25

GMAT Probability Questions: MCQs

  1. There are these two sets of letters, and you are going to pick exactly one letter from each set.  What is the probability of picking at least one vowel?
  • Set #1 = {A, B, C, D, E}
  • Set #2 = {K, L, M, N, O, P}

A. ½ 

B. ⅓ 

C. ⅙ 

D. ⅚

  1. Suppose you flip a fair coin six times.  What is the probability that, in six flips, you get at least one head?

A. 13/16  

B. 15/16 

C. 31/32 

D. 63/64 

  1. John has on his shelf four books of poetry, four novels, and two reference works.  Suppose from these ten books, we were to pick two books at random.  What is the probability that we pick one novel and one reference work?

A. ⅕ 

B. 8/45 

C. 3/10 

D. 5/2  

  1. In a drawer, there are 4 white socks, 3 blue socks, and 5 grey socks. Two socks are picked randomly. What is the possibility that both the socks are of the same color?

A. 1 

B. 17/21

C. 13/17

D. 19/66

  1. In a pack of a dozen candies, four candies are orange flavored. If a kid randomly picks two candies from the pack, what is the probability that the kid has no orange-flavored candy?

A. 1/7   

B. 2/11

C. 14/33

D. 7/33

  1. Of 200 people surveyed, 80 percent own a cellular phone and 45 percent own a pager. If all 200 people surveyed own a cellular phone, or a pager, or both, what percent of those surveyed either do not own a cellular phone or do not own a pager?

A. 35%

B. 75%

C. 55%

D. 65%

  1. When 22 people are selected at random from a group of 44 females and 44 males, what is the probability that at least one female is selected?

A. 5/14  

B. 7/14 

C. 9/14

D. 11/14

  1. Two dice are tossed once. The probability of getting an even number at the first die or a total of 8 is

A. 20/36

B. 3/36 

C. 11/36

D. 29/36

  1. A small company employs 3 men and 5 women. If a team of 4 employees is to be randomly selected to organize the company retreat, what is the probability that the team will have exactly 2 women?

A. 1/14 

B. 1/7 

C. 2/7 

D. 3/7 

  1. From a jar containing 4 red and 2 white marbles, Lionel draws two marbles simultaneously and at random. What is the probability that he picks one marble of each color?

A. ⅗ 

B. 8/15 

C. 7/15 

D. ⅖ 

Answers 

  1. D
  2. A
  3. A

GMAT Probability Practice Questions

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Some of the question formats are frequently asked in the GMAT. By regularly practicing the sample questions you will be able to increase both your efficiency and your accuracy. Here are a few sample questions that you can practice.

Question 1: In how many ways can the letters of the word “Octopus” be re-positioned in a way that the vowels appear together?

Question 2: 5 coins are tossed simultaneously. What is the probability of getting heads 3 times?

Question 3: If the probability of rain in Mumbai is 10 percent, what is the probability that it does not rain on the 3rd day in a 7 day period?

Question 4: A startup company employs 5 men and 7 women. 4 employees have to be selected for a company event, what is the probability that the team will consist of 2 women employees?

Question 5: A multinational company has 70 female employees and fifty male employees. For the Independence Day event, 4 employees have to be chosen, what will be the probability that the chosen team will consist of 2 female employees?  

Question 6: In a society, there are 300 female employees and a hundred male employees. it is analyzed that 20% of the female employees have higher-level degrees whereas only 10% of the male employees have higher-level degrees. If the secretary of society picks up a person, what will be the probability that the person will have a higher level degree and is a male?

Question 7: During a bet, Rajesh tossed a fair coin 4 times. What is the probability that he will get at least 2 tails?

Question 8: A company is sending joining letters to four different candidates. For 4 different letters, different envelopes with the correct address are made. The receptionist will be putting those 4 letters into the 4 envelopes randomly, what will be the probability that only one letter will be put in the envelope having the correct address?

Question 9: If we rearrange the letters of the word ‘PROBABILITY’, what will be the probability that the position of the consonants that are there in the world will remain unchanged?

Question 10: Each of the 25 balls in a certain box is either red, blue or white and has a number from 1 to 10 painted on it. If one ball is to be selected at random from the box, what is the probability that the ball selected will either be white or have an even number painted on it?

Question 11: A jar contains 8 red marbles and y white marbles. If Joan takes 2 random marbles from the jar, is it more likely that she will have 2 red marbles than that she will have one marble of each color?

Question 12: Terry holds 12 cards, each of which is red, white, green, or blue. If a person is to select a card randomly from the cards Terry is holding, is the probability less than 1/2 that the card selected will be either red or white?

Question 13: A box contains 10 light bulbs, fewer than half of which are defective. Two bulbs are to be drawn simultaneously from the box. If n of the bulbs in a box is defective, what is the value of n?

Question 14: 10 members of society, including members A and B, attended a meeting. 2 of these members were selected to form a committee. What is the probability that the 2 members selected were members A and B?

Question 15: Stacey needs to guess the last 3 questions of a quiz. Each question has 5 answer choices, one of which is correct. What is the probability that she gets at least 1 of the questions correct?

[BONUS] GMAT Exam Pattern

We understand that preparing for the GMAT can be a stressful process but with the help of the experts at Leverage Edu you can come up with a plan to tackle these challenges so that nothing comes between you and your dream college. 

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