Laran Evans
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Category Archives: Puzzles

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Number Series #1

By laran | Published: 2007/10/31

The Problem

What are the next two numbers in this series? This is a purely arithmetic series.

30, 33, 42, 50, 55, 80, 88, 152, 162, 174, ?, ?

Posted in Puzzles | Tagged Puzzles | 2 Comments

Bridge Crossing

By laran | Published: 2007/10/31

The Problem

There are 4 women who want to cross a bridge. They all begin on the same side. You have 17 minutes to get all of them across to the other side. It is night. There is one flashlight. A maximum of two people can cross at one time.

Posted in Puzzles | Tagged Puzzles | Leave a comment

Four Jars of Pills

By laran | Published: 2007/10/31

The Problem

You have 4 jars of pills. Each pill is a certain weight, except for contaminated pills contained in one jar, where each pill is weight + 1. How could you tell which jar had the contaminated pills in just one measurement?

Posted in Puzzles | Tagged Puzzles | Leave a comment

50/50 Marbles

By laran | Published: 2007/10/31

The Problem

You have two jars, 50 red marbles and 50 blue marbles. A jar will be picked at random, and then a marble will be picked from the jar. Placing all of the marbles in the jars, how can you maximize the chances of a red marble being picked? What are the exact odds of getting a red marble using your scheme?

Posted in Puzzles | Tagged Puzzles | 1 Comment

San Francisco Scramble

By laran | Published: 2007/10/30

The Problem

The San Francisco Chronicle has a word game where all the letters are scrambled up and you have to figure out what the word is. Imagine that a scrambled word is 5 characters long:

  1. How many possible solutions are there?
  2. What if we know which 5 letters are being used?
  3. Develop an algorithm to solve the word.
Posted in Puzzles | Tagged Puzzles | Leave a comment

Rope Burns

By laran | Published: 2007/10/30

The Problem

A rope burns non-uniformly for exactly one hour. How do you measure 45 minutes, given two such ropes?

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Two Trains

By laran | Published: 2007/10/30

The Problem

One train leaves Los Angeles at 15mph heading for New York. Another train leaves from New York at 20mph heading for Los Angeles on the same track. If a bird, flying at 25mph, leaves from Los Angeles at the same time as the train and flies back and forth between the two trains until they collide, how far will the bird have traveled?

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Six Shoes and Twenty-Four Socks

By laran | Published: 2007/10/30

The Problem

You are in the dark, and on the floor there are six shoes of three colors, and a heap of twenty-four socks, black and brown. How many socks and shoes must you take into the light to be certain that you have a matching pair of socks and a matching pair of shoes?

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Ten Gnomes

By laran | Published: 2007/10/30

The Problem

Ten gnomes are about to be executed. Although they don’t like the idea, they are each selfless and want to do anything (even by sacrificing themselves) in order to help their fellow gnomes. They are told what will happen to them: They will each be lined up single file, so that they are each facing the gnome in front of them. Each of them will be given a red or a white hat on their head, and from the back of the line (the gnome who can see everyone else) they will ask him to state his hat color, ‘red’ or ‘white.’ If he can state it correctly (he cannot see his own hat, only those in front of him), he is allowed to live. Knowing what is going to happen to them, they are allowed to devise a strategy beforehand. How many people can they guarantee to save, and what strategy will ensure this? (There are NOT five reds and five whites necessarily!)

Posted in Puzzles | Tagged Puzzles | Leave a comment

One From Five and Three

By laran | Published: 2007/10/30

The Problem

A milkman has two empty jugs: a three gallon jug and a five gallon jug. How can he measure exactly one gallon without wasting any milk?

Posted in Puzzles | Tagged Puzzles | Leave a comment
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  • About Me

    I've got a masters degree in computer science and over 10 years of experience building web-based systems using Java/J2EE, Ruby, Rails and PHP. I'm a strong believer in the effectiveness of Agile Methods. Read more »

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