# How NOT to Do Math [Video]

The following video is a funny example of how NOT to do math in a case interview. The math question is:

"If you're traveling 80 miles per hour, how long does it take you to travel 80 miles?"

See one person's answer (who by the way should NOT work in consulting).

Note: This video has gone viral on YouTube and has been seen by over 4 million people.

The person featured in the video seems very nice and ernest. Needless to say, the math skills demonstrated aren't strong enough for consulting work. One lesson to take away from all this is to know what you're good at (and not) and build a career around your strengths (not your weaknesses).

• Jeremy Kim Mar 24, 2012, 4:13 am

Two things:
(1) Why is he driving and recording a video at the same time? Quite dangerous!
(2) Can you imagine trying to do consulting for her? She probably would take forever to convince in terms of the validity of your math.

• Thao Tran Mar 24, 2012, 10:20 am

Well, sometimes we usually make everything more complicated for simple prob

• Israel Mar 24, 2012, 1:08 pm

My ingoing hypothesis… is that she has a mental handicap.

Although I got snagged on a math problem in my last interview trying to calculate a percentage, and the interviewer even commented that I seemed to be struggling. I tried to just stay open and friendly, and said “Hmm.. yeah I’m doing something wrong here. Is it ok if I guestimate?” I got the offer, so I think when you find yourself messing up, if you acknowledge it and move on, that helps.

Also, she’s thinking too hard and missing a great view! I love that drive to Logan.

• James Mar 24, 2012, 1:42 pm

She simply misunderstood the question. I can tell that she is trying to calculate how long it would take for her to run 80 miles.

• Victor Mar 24, 2012, 2:15 pm

Here’s the back story on this video. The couple had just finished college exams and the woman had only a few hours of sleep.

Lesson #1 – when you’re tired your mind deteriorates

Lesson #2 – while I might look like she’s not strong in math or she made a math mistake, it’s actually unclear (though I have my suspicions). What is clear was she was not LISTENING very well. Even if she did not understand math, the guy essentially gave her the answer IN the question itself. She could have attempted to paraphrase the question to confirm her understanding of the question and perhaps realize in the process the answer was already provided.

A lot of case interviews get blown by the candidate from not listening very well or misunderstanding something. Always, always, always take the extra 20 seconds to verify your understanding of the situation before trying to solve a problem.

Lesson #3 – keep it simple. She was making the problem WAY more difficult than it needed to be. I find candidates will do this when they are nervous or under stress. Sometimes something simple is actually just that simple.

One of the reasons case practice is useful is because it helps you overcome the natural anxiety in the first few seconds after hearing a case, to calm down, and to THINK.

Incidentally, the initial anxiety still happens to me all the time. Sometimes my readers will email me a case they aren’t sure how to solve. In the first 15 seconds after hearing the case, my gut reaction is two fold… A) I have no idea!, B) quickly say outloud… “hmmm, that’s interesting….” (aka stall).

Then I can calm down… And usually still don’t know what to do, but think pick a hypothesis…and say it s-l-o-w-l-y, the I ask myself “what must be true for this hypothesis to be true” and then I get into the swing of things and am able to structure the problem.

So the big takeaways from this video are get a good nights sleep and LISTEN carefully,

Victor

• Raj Subramanyam Mar 25, 2012, 11:16 am

This video is hilarious and was just put out for fun.
Years ago, we had a question posed during lunch, which went like this: Christopher Columbus made three trips to discover America and he died on one of those trips. On which trip did he die?
Needless to say, one guy in our lunch group started over-thinking and became the butt of the joke for every lunch session. This almost went on for two months! He thought this was a trick question and said that we had concealed information such as did he die on land or at sea, which America, are you sure Columbus discovered America, etc.
To this day we still remember that question and the endless fun we had. Pity, we could’nt record it at the time.
The answer (not-so-obvious to some) by the way is: Columbus died on his last trip

• Leonardo Apr 30, 2012, 12:39 pm

Except that Columbus could not have “discovered” America three times… He “discovered” America during his first trip only… 😉

So maybe the answer to Raj could have been none…