The Insider’s Dossier The Insider’s Dossier

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How many Smarties fi t in a car?

Brain teasers are popular with consulting fi rms, fi nancial institutions,

the industry and even start-up companies as a recruitment test tool

for top jobs.

Whether you’ve bought this book specifi cally to prepare for a job

interview, or simply as an intellectual challenge – this book

provides you with a comprehensive collection of ambitious

problems together with their solutions.

This defi nitive training resource will provide you an intelligent and effi cient

approach to solve all kinds of brain teasers – 140 problems included.

Challenge yourself! Topics covered:

• Mathematical Thinking

• Logical Thinking

• Trial and Error

• Thinking „Outside the box“

• Guessing

For additional job interview preparation, we recommend „The Insider’s Dossier: Recruitment Test at Top Companies. Tests on Logic, Analytics and Intelligence“. (Available in German only)

Brain teasers & puzzles in Job Interviews

140 interview problems

The

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more brain teaser tests on

www.squeaker.net

With all-new brain teasers

ISBN 978-3-940345-27-1

€ 19,90

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The Insider’s Dossier: Brain teasers & puzzles in Job Interviews

140 interview problems

2

The Insider’s Dossier: Brain teasers & puzzles in Job Interviews140 interview problems

squeaker.net

www.squeaker.netkontakt@squeaker.net

Copyright 2013 by squeaker.net GmbH, Cologne, Germany

Publisher: squeaker.net GmbHEditor: Stefan Menden, Jonas SeyfferthEditorial contributors: Michael Hoi, Maya Lischke, Stefan Menden,

Jonas Seyfferth

Orders: Through your bookstore or freepost from squeaker.net/insider.

ISBN: 978-3-940345- -

In spite of careful research, neither the publishers, nor the editor or authors can be held responsible for the contents of this text. Please send any comments and suggestions to: kontakt@squeaker.net.

Please do not copy or distribute. All rights reserved, including the rights to copy, distribute and translate. No part of this publication may be stored, saved, copied or distributed without prior permission from the publisher. Come on: buy your own copy to ensure that we can continue to keep up the good quality!

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Contents

Introduction 7

What is a brain teaser? 8 The Golden Rules 12

Chapter 1: Mathematical Thinking 13 1. The inspector and the time of day 13 2. An outing in a horse and carriage 15 3. Family members 16 4. The cheese 17 5. Regular trains 18 6. Twins at the station 18 7. Danger! 21 8. The disappearing dollar 22 9. Join the club 23 10. Processing steel plates 25 11. Half a chicken 26 12. The clock hands 26 13. The 32-sided shape 27 14. Bus route number 1 28 15. The red ball wins 29 16. Game show winner 30 17. The wine cellar 31

Chapter 2: Logical Thinking 33 18. Days of the week 33 19. The only child and the oil painting 33 20. The inspector and the burglary 34 21. Weighing nine balls 35 22. Weighing twelve balls 36 23. Cowboys and Indians 38 24. Unfaithful husbands 40 25. Truth and lies 41 26. The insurance rep 42 27. Shake hands 43 28. The birthday party 44 29. The pirate’s treasure 45 30. Which pet? 46

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Chapter 3: Trial and Error 49 31. Arithmetic 49 32. Hourglasses 50 33. Scooping up water 50 34. Escape from the cave 51 35. The cannibals’ island 52 36. The shepherd 53 37. Missed the train 54 38. The cruise 55 39. The bus journey 55 40. The bread factory 56 41. The interview 57

Chapter 4: Thinking Outside the Box 59 42. The rope ladder 59 43. Sock chaos 60 44. Multicolored buttons 60 45. Burning ropes 61 46. The light bulb 61 47. God and the devil 62 48. The operation 62 49. Dr. Andrews 63 50. The badminton tournament 64 51. Crossing a river 64 52. The lost gold 65 53. Death penalty 66 54. Fritz the dog 67 55. Paper games 68 56. Blocked pipes? 69 57. Ice cream and trouble 70

Chapter 5: Estimation 71 58. How many dogs? 73 59. Cleaning your teeth 74 60. Weddings 76 61. Weighing Manhattan 77 62. A department store’s profit 78 63. Santa is stressed 80 64. How many reindeer? 80 65. How many Santas? 81 66. Smart Smarties 81

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Chapter 6: Other tests of your logic 83 67. Numerical sequences 83 68. Graphic sequences 84 69. Analogies 85 70. Generic terms 86 71. Bridges between two words 86 72. Looking for a subject 86

Chapter 7: Solving Brain teasers Alone 87 73. Buying livestock 87 74. The lonely cowboy 87 75. The raw egg 87 76. The mountaineer 87 77. How many threes? 88 78. Taking a walk 88 79. Bear hunting 88 80. The glass container 88 81. The hands of the clock 88 82. Men from Mars 88 83. Time 88 84. The high-speed bird 88 85. The water level 89 86. The speed of a snail 89 87. The drain cover 89 88. In Vino Veritas 89 89. One hundred cupboards 89 90. Adam and Eve 89 91. The egg timer 90 92. Folding a sheet of paper 90 93. The managers’ holiday 90 94. Bicycles 90 95. The girl group 90 96. Ageing fast 91 97. The lock 91 98. Mistake in calculation 91 99. The desert researchers 91 100. How old is Agnes? 91 101. The beautiful princess 91 102. Number games 92 103. Euros in the stadium 92 104. Talking shop 92 105. Royal wedding 92 106. Blond beauty 92 107. Watery cucumber 92 108. The dice game 93

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109. Poisoned wine 93 110. At the bus stop 93 111. The coin game 93 112. Average earnings 93 113. The bookworm 94 114. An alphabetic mess 94 115. Chocolate bars 94 116. Better safe than sorry 94 117. The swimmer 94 118. The abbey 94 119. The good businessman 95 120. Busy gardeners 95 121. Crossing hands 95 122. Crossing the sea 95 123. How old is the child? 95 124. Decoding 95 125. Fishing for guppies 95

Solutions to Chapter 7 97

The Ten Most Popular Brain teasers 110

Even More Brain teasers 111 126. Cooling down liquids 111 127. The price of a Panini sticker album 111 128. Filling a swimming pool 111 129. In the rain 111 130. Average speed 111 131. Freight train 111 132. Transporting bananas 112 133. Drawing a circle 112 134. Lotto 112 135. The rower and the dog 112 136. The sum 10 112 137. Witch’s test 112 138. Water of the earth 113 139. Weight on the moon 113 140. Beetles in a circle 113

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Introduction

Congratulations on becoming the proud owner of the international version of the book »The Insider’s Dossier: Brain teasers & puzzles in Job Interviews – 140 Interview Problems«. Whether you’ve bought this book as preparation for a job interview, or simply as an intellectual challenge, we’ll introduce you to the most popular brain teasers used by some of the world’s leading organizations.

This book aims to help you solve brain teasers successfully. But at the same time, it’s more than just a guide for job hunters. With practice, you’ll see that it can be great fun getting your head around tricky problems and training your mind to deal with all sorts of scenarios, whether or not you’re attending a job interview in the near future.

The problems in this book are mainly those used by consulting com-panies, banks, companies from the consumer industry, as well as tech companies and business schools. Some have already been discussed within the framework of the online career network squeaker.net or nicube.com. Others have been researched from companies and job hunters and we’ve developed some suggestions for solutions ourselves.

Thanks to the online career networks squeaker.net and nicube.com, we’re able to ensure that our book provides up-to-date examples and information about the sort of tests you’ll be faced with at interview. The amount of information in the networks prove that brain teasers have become a regular part of interviews, and are more and more frequently becoming part of the standard procedure when it comes to banks, consulting and tech companies.

If you know more brain teasers, or alternative solutions, feel free to share and discuss them with us in the network: à squeaker.net.

We hope this book provides you with many hours of fun – and ultimately career success!

The squeaker.net editorial team

Note: These types of brain teasers are used by international organizations throughout the world. Whilst most of them come from US companies, the same questions are asked in Germany, the UK, India, China, France, Australia, Dubai, South Africa, Spain, or wherever. Whilst details may vary, the main methods of reaching the solutions are the same. Due to the international nature of this book, we use metric measurements in the examples. In an interview in your home country, expect whichever measurements are usually used in your country to be used.

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What is a brain teaser?

Brain teasers are logical problems which test your ability for ana-lytical, autonomous and logical thinking. They’re usually in the form of a short anecdote and encourage you to use your ability to solve problems in an unknown, unusual and possibly even totally unreal situation. In many ways, brain teasers are like mathematical problems that we all remember from school: you use your every-day knowledge and your logical ability to solve an abstract problem.

What’s fun and intellectually challenging is the fact that, at first, brain teasers seem impossible to solve (or at least impossible to solve correctly), and yet all of them have a logical solution. Once you’re set before a brain teaser, you just have to find out the answer!

Why do organizations use brain teasers?Certain types of organizations regularly use brain teasers for job inter-views. Watch your friends try and solve a brain teaser. In no time at all, you’ll notice their individual ability and motivation and how diffe-rently each of them goes about solving the brain teaser. This is exactly what HR wants to do when using a brain teaser in an interview: they want to see how you deal with a tricky problem, and whether you can analyze it and deal with it in a structured manner.

At the same time, recruiters can determine how a candidate copes with the stress of a difficult, unusual situation, and how he or she expresses himself: i.e., not only is the candidate able to understand, structure and solve the problem, but can also explain it to others. Brain teasers also give the interviewer an idea of how the candidate copes when he or she doesn’t immediately find a solution to the problem.

Brain teasers sometimes serve as an alternative to intelligence tests, allowing companies to test the mental ability of candidates. Whether or not they’re really a suitable alternative is a bone of contention.

For organizations, however, brain teasers have the advantage of not only allowing them to test the candidate’s general intelligence, but also of showing them whether this person is actually in a position to be able to solve and deal with real problems. What they’re looking for is the basic ability to solve problems rather than the specific quali-fications that may be required for the job.

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Which organizations are likely to use brain teasers?Brain teasers at the level we’re looking at in this guide tend to be used for candidates with a university education. They’re most often used for recruitment within the investment banks but are also frequently used by consulting companies. You can also expect brain teasers for any position involving autonomous, analytical skills: that may be in marketing, in the tech area or in logistics, as well as in controlling or finance. We’ve also heard of brain teasers sometimes being used by private universities and business schools, as well as some start-up companies.

Depending on what sort of a job you’re applying for, companies may also require certain professional or subject-related qualifications without which you’d be unable to solve the problems they put before you. As a business or economics graduate, for example, you should be able to calculate turnover and profit. And if you’re applying for a position in programming, then it’s fair to assume that your employer will expect a greater depth of mathematical ability than for your average candidate.

But not all consulting companies and banks use brain teasers. Don’t be disappointed if you don’t get one at interview: they will rarely play a major role in the recruitment process. But, of course, if you’re lucky enough to be given the opportunity to shine, then why not do it?

How do I best deal with brain teasers?Candidates require a variety of skills to solve brain teasers. Companies want to test mathematical understanding, logical thinking, crea-tivity and the ability to think out of the box. Most brain teasers can be solved without any specialist knowledge or expertise. It’s rare for companies to be looking for mathematical formula or scientific laws. But no matter what the problem, it’s possible to practice the right way to deal with these types of problems.

When using brain teasers, organizations are looking for candidates’ ability to think in unusual ways. You’ll very rarely be able to find the solution immediately, and watch out if you do, because it’s probably wrong! Indeed, the more obvious the answer, the more likely it is to be wrong. Some sort of trick will nearly always be hidden in the text. That doesn’t mean that you can’t express the obvious answer in an interview: just don’t forget to mention that you think it’s probably not the correct one. Then go on and look at why the answer is wrong and start structuring the problem in hand.

Often, the candidate will get heaps of information in a brain teaser that’s totally irrelevant. By the same token, the really relevant information may be hidden in a seemingly unimportant sentence or word. Sometimes, the difficulty of the brain teaser is the way we

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unintentionally interpret information into a text which isn’t even there because it just seems so obvious to us. Thus, the most important first step is to have a really good look (or listen) to the problem and check the content and relevance of every single word.

It’s also not only important to read the text of the brain teaser very carefully, but also to continuously check every step. If you’ve solved a mathematical problem, then check it again to make sure that you’ve taken into account all the circumstances, and check whether your formula really was correct. And when you’ve done that, check that your correct answer does actually makes sense, or whether there may be other physical restrictions which aren’t mentioned in the text but implied, or simply to be expected in reality. For example, you’ll see in one problem in this guide that whilst it’s possible to make a dog run at the speed of light using mathematical formula, this isn’t feasible in reality!

But don’t get too disheartened if you don’t really understand the brain teaser: the stories used are often pretty absurd. Don’t get put off because reindeers suddenly start flying, but just accept it as a given. And remember that, whilst companies are certainly looking for creativity, you shouldn’t let your imagination run wild by making assumptions that are not mentioned in the text, and you shouldn’t start taking routes that are obviously not being asked for!

Make sure you look for solutions and not just for mistakes in the question! You will always be given all the information you need to solve the problem.

Many brain teasers seem impossible to solve at first. Candidates may well be put off by questions which don’t make it clear whether there really is a solution to be found. Always assume, even with these questions, that there is an answer to the brain teaser. This is nearly always the case. If you really believe there is no solution, then make sure you can justify your case. Don’t be put off by open questions: just try and solve them using the strategies that we set out for you in the following chapters.

If you can picture several solutions to a brain teaser then go for the simplest one first. Usually, the solutions aren’t as complicated as you may imagine. Before you start with complicated mathematical calculations, check again whether there’s not an easier solution. The interviewer will almost certainly prefer the easier answer.

Try and solve the brain teasers in this guide on your own, without looking at the answers: even if this seems impossible at first. The ability to stick at it and the determination to solve complex pro-blems are important factors in solving brain teasers. Don’t look at our answers until you’ve found a solution for yourself.

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How do I solve a brain teaser in a job interview?Whether or not you find the correct solution to a brain teaser won’t count as much in a job interview as the way you deal with the problem. The interviewer wants to see whether you can go about things in a structured manner by thinking through complex problems without losing faith. Always remember the following tips and you’re already half way to solving a seemingly impossible problem.

Listen to the instructions very carefully and don’t hesitate to make notes. If there’s something you’re not sure about, make sure you clarify it straight away. Once you’ve understood the instructions properly, repeat the important points and watch the interviewer’s reaction. Take a minute to think about it: nobody expects you to provide a correct answer after a few seconds! On the contrary, you should take time to consider a brain teaser carefully. Consider all influencing factors and ask intelligent questions. Show how you can proceed in a structured manner without jumping from one thought to the next. Organize the problem into sub-problems. Suggest hypo-thesis and test out whether these actually help solve the problem. Think ideas through to the end, and if they prove wrong, just start again using a different method.

The most important thing in the whole process is to express your thoughts and various steps in finding a solution in a comprehensible manner so that the interviewer understands exactly what you’re thinking. It won’t help you at all to go off on your own for ten minutes and then suddenly come back with the answer.

Look at the process of solving the brain teaser as a form of inter-action between you and your interviewer. Watch your posture (no slouching!) and express yourself clearly. Don’t let yourself get nervous. At the end, summarize your most important steps and present your solution clearly.

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The Golden Rules

The ten most important rules for solving brain teasers in job interviews:

1. Never let yourself be defeated by the complexity of the problem. Remember that all brain teasers have a solution!

2. Sort out the important facts and try not to get distracted by trivial information.

3. If there’s something you haven’t understood, make sure to clarify it.

4. Look at the brain teaser analytically and don’t forget to use your common sense.

5. Try and picture the problem in your mind.6. Take the problem one step at a time, detailing your steps as

you go, and making sure your interviewer is aware of each and every step.

7. If you can’t find a way of solving the whole problem, try and work in small steps, checking your assumptions and creating hypotheses.

8. Nothing is worse than giving up too early. If your way of solving the problem isn’t working, then try a new way.

9. Try and have fun solving brain teasers rather than seeing them as a test.

10. If you’re given a brain teaser that you already know, ask to be given another.

In the following chapters, we’ve divided the brain teasers up into dif-ferent categories depending on which skills they’re testing, and which strategies are most useful to help you solve them successfully. It’s impossible, however, to categorize them absolutely clearly as many brain teasers can be solved using different strategies. For example, whilst a lot of brain teasers can be solved using mathematical formula, they can also be solved with logical thinking and trial-and-error. Thinking out-of-the-box is something you’ll need to be able to do for most brain teasers. At times, that will be the requirement for solving a brain teaser, but at other times you’ll also be able to solve the problem simply by noticing the trick in the question.

After the categorized examples, you’ll find more brain teasers which have not been categorized and which you should concentrate on working on yourself. You’ll find the answers at the end of the book. Enjoy!

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hsChapter 1: Mathematical Thinking

Although it may not seem like it at first, brain teasers are often just a matter of simple calculation. Most problems can be solved using basic mathematical skills and don’t really require any advanced mathe-matical knowledge. So even if numbers aren’t your strength, don’t despair if you’re asked about speed, angles and probability.

Whenever you’re asked directly for a number, whether it’s speed, distance, time, or a number of people, this is an indicator that you can find the exact answer by using one or more equations. At the same time, don’t forget that brain teasers aren’t math tests and are not being used to determine your mathematical capacity. If you think a question seems impossible, or at least impossible to solve without a calculator, there’s very probably another way of solving the question than the way you’re currently doing it! Start thinking outside the box and you’ll realize there’s usually a way of finding the solution which is easy to calculate. Always assume that the question contains all the information you need to be able to solve it. If you come to the conclusion that a brain teaser is impossible to solve with the infor-mation provided, then you’ve almost certainly missed something very important hidden in the question. The hard part is often filtering out the important information from everything else in the text, then separating it, and using it to create a useful equation. Have a look at this simple example to help explain what we mean:

1. The inspector and the time of day

»Good morning inspector«, said Mr. Smith »Could you tell me the time please?« »Of course«, replied Inspector Brown, »If you add a quarter of the time since midnight until now to half the time from now until midnight, then you’ve got the exact time.«

Have a think about it. The problem sounds confusing, but Inspector Brown has actually given you all the information you need to solve this brain teaser. The inspector expresses the time in an equation which you simply have to transfer into mathematical formula to get the answer. To do this, you need to be sure what he means by the terms »the time from midnight until now« and »the time from now until midnight«. »The time from midnight until now« is obviously

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the time you’re looking for. But »the time from now until midnight« can also help you work out the current time. Assuming there are four hours until midnight, the current time must be 8 p.m. If you turn this around, you’ll get the time until midnight by subtracting the current time from 24.

If x represents the amount of hours since midnight (i.e. the current time), and you take into consideration all the information given in the question, then the time you’re looking for can be expressed by the following equation:

x = — x + — (24 - x)14

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x = amount of hours since midnight

This equation expresses the exact information that Inspector Brown gave Mr. Smith. And now it’s easy to find out the exact time: you just have to solve the equation for x and then you get the answer:

x = 9.6

But watch out with the interpretation of the results! X = 9.6 doesn’t mean that it’s 9.06 a.m. but that it’s 9.6 hours after midnight. 0.6 hours is 36 minutes (60 minutes multiplied by 0.6). Now Mr. Smith knows exactly how late it is: it’s 9.36 a.m.

This is a good example of what’s important when solving this type of brain teaser. First of all, you need to realize that the problem can be solved mathematically. As an actual number is asked for in the question (in this case the time), that shouldn’t be too difficult. The second step is to filter out the important information from the text and put it into mathematical formula. Once you’ve managed this, you’ll get the answer you’re looking for simply by solving the equation or, as in the next example, by solving the sequence of equations.

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