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Monthly Archives for November, 2013



Generating a Random variable.

Posted on: November 10th, 2013 by
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Suppose you have a random number generator that generates a number uniformly between a and b. However, you do not know a and b. How do you generate a random number uniformly distributed between 0 and 1? You are only allowed a finite number of copies of Unif(a,b) random variables. - via Tom Courtade.

Measurement

Posted on: November 9th, 2013 by
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Measure 9 minutes using a 7 minute and a 4 minute sand-timer. -via old Google Interview Questions (Google stopped asking such brainteasers and riddles in interviews; now they only ask coding questions).

Limit of a function

Posted on: November 8th, 2013 by
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Suppose a function f(x) satisfies \lim_{n\rightarrow \infty} f(nx)=0 for all real x, where n is a natural number. Then show that \lim_{x\rightarrow \infty} f(x)=0. - via Sudeep

Intersection of a cuboid and circle

Posted on: November 7th, 2013 by
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You are given a cuboid in 3-D space, defined by the end-points of the diagonal (x1,y1,z1) and (x2,y2,z2) where x1<x2,y1<y2,z1<z2. You are also given the center (x3,y3,z3) of a circle and it's radius r. How will you test if the cuboid and the circle intersect? We want an elegant solution. - Via Cheuk Ting Li.

Escape from Blender:

Posted on: November 6th, 2013 by
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Suppose you are shrunk into the size of a nickel and placed inside a blender. Your shape and density remains unchanged. The blender's lid is open. In 60 seconds, the lid will close, and the blender will start. If you don't get out of the blender by then, you are doomed. Show how you will get out of the blender. Hint: This is a physics problem, Continue reading the story "Escape from Blender:"

Helium ballon inside a car

Posted on: November 5th, 2013 by
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A helium balloon is tied to a string inside a car. You secure the other end of the string to a point in the car. All windows in the car are closed. Now the car starts accelerating forward. Will the Helium balloon move forward, or move backwards or stay put? - via Google Interview questions available publicly on wired magazine

Crossing the desert

Posted on: November 4th, 2013 by
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It takes 6 days to cross the desert. However, you can only carry food and water supplies for 4 days. You are allowed to hire as many helpers as you can. Each helper can only carry food and water for 4 days and each helper has to eat and drink himself too. How will you cross the desert? None of your helpers should die in Continue reading the story "Crossing the desert"

Pasturage problem

Posted on: November 3rd, 2013 by
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If 12 oxen eat up 3 and 1/3 acres of grass in 4 weeks, and 21 oxen eat up 10 acres in 9 weeks, how many oxen will eat up 24 acres in 18 weeks; the grass being at first equal in every acre, and growing uniformly? Note: If you have not yet tried to solve this problem, do try, particularly in the 19th-century arithmetical Continue reading the story "Pasturage problem"

cable car crossing

Posted on: November 2nd, 2013 by
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If you travel in a cable car from one end to another, what fraction of the cars do you pass on the other side? Cable cars - via Programming interviews exposed

Come back to where you started

Posted on: November 1st, 2013 by
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You go 1 mile south, then 1 mile east and finally 1 mile to the north. You come back to where you started. One way to achieve this is starting from the north pole. But there are other ways to achieve this. Can you find 3 other ways to achieve this feat of coming back to the starting point after executing the stated moves? - via Continue reading the story "Come back to where you started"

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