Medium puzzles




Medium Probability

A line of 100 airline passengers is waiting to board a plane. They each hold a ticket to one of the 100 seats on that flight. For convenience, let's say that the nth passenger in line has a ticket for the seat number 'n'. Being drunk, the first person in line picks a random seat (equally likely for each seat). All of the other passengers are sober, and will go to their proper seats unless it is already occupied; If it is occupied, they will then find a free seat to sit in, at random.
What is the probability that the last (100th) person to board the plane will sit in their proper seat (#100)?

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Medium Probability

A stick is broken into 3 parts, by choosing 2 points randomly along its length. With what probability can it form a triangle?

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Source: Quant Interview
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Medium Discrete Maths

A rabbit sits at the bottom of a staircase with n stairs. The rabbit can hop up only one or two stairs at a time. What kind of sequence is depicted by the different ways possible for the rabbit to ascend to the top of the stairs of length n=1,2,3...?

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Medium Discrete Maths

A. B & C live together and share everything equally. One day A brings home 5 logs of wood, B brings 3 logs and C brings none. Then they use the wood to cook together and share the food. Since C did not bring any wood, he gives $8 instead. How much to A and how much to B?

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Source: CSEblog
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Medium Strategy

Suppose you have a hotel which has one floor with infinite number of rooms in a row and all of them are occupied.
1) A new customer wants to check in, how will you accommodate her?
2) What if infinite number of people want to check in, how will you accommodate them?
3) Suppose infinite number of buses arrive at the hotel, each having infinite number of people, how will you accommodate them?

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Source: CSEblog
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