Case_In_Point_7th_Edition_Page001_183_2

The Bags ¦f p ¦§¨
There are three bags of gold. One of the bags contains fake gold. All the bags and all the
coins look exactly alike. There is the same number of coins in each bag. The real gold coins
weigh one ounce each, the fake coins weigh 1.1 oz. apiece. You have a one-pan penny scale
and one penny, which means you can weigh something just once. (You load the scale, put the
penny in, and the scale spits out a piece of paper with the weight.) How can you tell which bag
has the fake gold?
You take one coin from the first bag of gold, two coins from the second bag and three coins from
the third bag. Place them all on the scale. If the coins weigh 6.1 oz., then you know that the first bag
held the fake gold. If they weigh 6.2 oz., then it is the second bag. If the coins weigh 6.3 oz., then the
third bag held the fake gold.
There are numerous puzzle and brainteaser books to be found in your local bookstore. If you are worried
about these types of questions, you may want to pick up one of these books.
M arket -si z g iQn
uest ©ns i
Market-sizing questions surface all the time and can be found during any round of interviews and within
many larger business case questions. The back-of-the-envelope question received its name because
the questions used to start with, “You’re on an airplane with no books, phone or any other resources. On
the back of an envelope, figure out...” You’ll find some of these questions intriguing; some will be fun,
others preposterous. However, it’s important to have the “rip right through it” look in your eyes; at least
pretend that you’re having fun.
Oftentimes during market-sizing questions, all you have to work with are logic and assumptions. There
are going to be instances when your assumptions are wrong. Sometimes the interviewer will correct you;
other times he will let it go. The i nerv t ew i er is m©re i nereste t i ny©ur can ©gi th©ughtpr©cess
than w hether y©ur answ er is c©rrec t If . you are still concerned, you can always say, “I’m not that
familiar with this market, so if my assumptions are off, please correct me.” Ninety percent of the time, the
interviewer will tell you not to worry about it. Everything you say has the potential to be questioned — be
ready to stand behind your assumptions. Your assumptions should be based in some sort of logic. If you
just pull them out of the air, you’re risking the interviewer aggressively challenging your assumptions and
your credibility.
MARKET-SIZING QUESTIONS
Your answer should be based on logic and assumptions.
S ru t c re t u
Listen to the question, then determine the type of case, population based, household, general
population or preposterous.
Ask clarifying questions only if you don’t understand the question or terminology.
Lay out your structure first and the steps you’ll need to answer the question; then go back through it
with the numbers.
A ssu m
©ns p t i
Don’t worry if your assumptions are off; the interviewer is more interested in your thought process