Case

# Brainteaser: Birds on train

3,2 Tsd. mal gelöst
Schwierigkeit: Fortgeschritten | Stil: Brainteaser | Themen: Brainteaser

## Problemdefinition

Assume we have two trains moving on the same track. These trains are approaching each other head-on meaning that Train A is moving towards Train B & vice versa. The track these trains are on has a distance of 120 km. Train A has a speed of 26.6 km/hour and Train B has a speed of 19.7 km/hour.

Now on top of Train A, there is a little bird that is flying with a speed of 33.4 km/hour. The bird flies from Train A to Train B and back. He keeps doing this until both trains approach each other.

The question is: How much distance has the bird flown once both trains approached each other?

## Kommentare

Brain Teasers are short questions with difficult logical or creative answers. They are a good way to test your analytical skills and capacity to think out of the box. These short questions also show the interviewer your ability to elaborate on difficult tasks from the real world. Each Brain Teaser is supposed to be solved by the interviewee in about 5-10 minutes.

If the interviewee gets stuck in a brain teaser (i.e. spends more than 10 minutes), propose to go on to the next one.

## Detaillierte Lösung

Step 1: Sum up the speed of both trains and divide the total distance of 120 km by the summed up speed.

26.6+19.7=46.3 km/hour.

120 km/46.3 km=2.6 hours which is about 2 hours and 40 minutes. Feel free to round up and estimate here.

Step 2: Now that we know how long it will take before the two trains reach each other, we can calculate the distance the little bird has flown.

2.6 hours*33.4 km=87 km.

Conclusion: In the timeframe of 2.6 hours the bird flies a distance of 87 km back and forth until the trains reach each other.

Verwandte Consulting-Fragen

Hey, I am new to this too, but I think I have some ideas for your problem. Your approach looks good, but I think you have a mistake in how you time the trains. You say that there is one train e... (mehr)

Beste Antwort bisher:

Hi Anonymous, there may be several reasons for that; some of them, in order of frequency, are: Your structure is not complete enough – you are just using not MECE/ not complete structure... (mehr)

Beste Antwort bisher:

Hi Anonymous, first of all - this is not a brain teaaser, but an ordinary estimation question! Here is a high-level approach: I would start with the second question, because it is most straight forw... (mehr)

Bisher beste Antwort von 3 Antworten:

Hey there Here is one approach: # Hair Salons = (# hours required for men's haircuts per year + # hours required for women's haircuts per year) / average service capacity of 1 hair salon (which... (mehr)

Bisher beste Antwort von 2 Antworten:

Hi, here's how I would approach it - Define the geographic area to be covered [the whole world? the U.S.? NYC? Manhattan?...for this example I'll use Manhattan] - Population living there [~ 1... (mehr)

Verwandte BootCamp-Artikel

## Typical Question Types in Written Tests

Questions among all tests can be categorized in math, GMAT-style, chart reading and brain teaser questions. Each type needs to be approached differently.

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## Brain Teasers

Learn how to tackle brain teasers and what purpose they serve in consulting case interviews

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