technology and zen of life

“A heisenbug (named after the Heisenberg Uncertainty Principle) is a computer bug that disappears or alters its characteristics when an attempt is made to study it.”

Puzzle 6: What’s the radius of the circle?


A simple geometry problem. Shouldn’t take more than a minute to come up with the answer.

After all we all know the radius of the circle is pi*r^2. right ?

The following diagram (not to scale) shows a circle with the center at point C. What is the radius of the circle?


Give proper explanation with your answer.

Puzzle 5: Burn the rope..

A classic puzzle involves being given 2 ropes and a lighter. The burning of one rope from end to end takes 1 hour, however the ropes do not burn in a uniform manner (ie: if you light it at one end, the first half of the rope could burn through in one minute while the second half may take 59 minutes to burn). Your goal is to measure out 15 minutes using the two ropes and the lighter.

You can assume that lighting a rope takes zero time.

Hint: You can break the rope with your bare hands..

Best Solution by Dark

using a single rope

it takes 1hr to burn the whole rope
rope is not burning evenly

break the rope in 2 parts (sizes don’t matter), part A and B

burn both the parts A and B from both sides.

as the ropes burn unevenly, let say A is burnt, and B has still unburnt part.

At the moment A is finished start a new fire somewhere in mid of B, thus making 2 new parts of ropes, lets say A’ and B’

if you continue this and the rope has 4 burnings ends always.. you can measure 15 mins using a single rope (assuming burning takes 0 time)

About the 2nd rope.. just burn it or timepass :D

Puzzle 4: The Two Switches

The warden meets with 23 new prisoners when they arrive. He tells them, “You may meet today and plan a strategy. But after today, you will be in isolated cells and will have no communication with one another.

“In the prison is a switch room, which contains two light switches labeled A and B, each of which can be in either the ‘on’ or the ‘off’ position. I am not telling you their present positions. The switches are not connected to anything.

“After today, from time to time whenever I feel so inclined, I will select one prisoner at random and escort him to the switch room. This prisoner will select one of the two switches and reverse its position. He must move one, but only one of the switches. He can’t move both but he can’t move none either. Then he’ll be led back to his cell.

“No one else will enter the switch room until I lead the next prisoner there, and he’ll be instructed to do the same thing. I’m going to choose prisoners at random. I may choose the same guy three times in a row, or I may jump around and come back.

“But, given enough time, everyone will eventually visit the switch room as many times as everyone else. At any time anyone of you may declare to me, ‘we have all visited the switch room’ and be 100% sure.

“If it is true, then you will all be set free. If it is false, and somebody has not yet visited the switch room, you will be fed to the alligators.”

Mail your answers to gurus [dot] comments [at] gmail [dot] com

Also comment if you have mailed the answer.


This problem is taken from a site which I will put up later, so that you don’t ruin the problem by looking at answer. Till then you brainstorm. It’s an awesome problem.

Puzzle 3: Weigh ’em Up!!

This one is simple…

You have eight balls and a balancing pan (the one on which you have two pans and can compare weights), one of the eight balls is either heavier or lighter than the rest. The remaining 7 have the same weight. How many least no of weight comparisons will it take to find out the defective ball and also weather it is heavier or lighter.
Also tell how you achieved at the number… mail your detailed reply’s to gurus [dot] comments [at] gmail [dot] com and put up the least number you required here as a comment 🙂

Solution (by ross):

put 2 balls on each side(1st weigh), if they balance put them to one side and mark as OK if they don’t balance then mark the other 4 as OK.

take 3 of the 4 NOT OK balls, put 2 on one side and 1 on the other with 1 of the balanced balls (2nd weigh). if they balance the only ball that hasn’t yet been on the scales is DEFECTIVE, weight it against one of the OK balls(3rd weigh) to see if it’s heavier or lighter…

if the balls don’t balance on the second weigh then take the known OK ball and the one that you put with it (let’s call it ball A) off then weigh (3rd weigh) the other 2 balls (call them B & C). If B & C balance then A is the defective ball. We now know that B & C are OK balls so if A & OK were heavier on the 2nd weigh then A is HEAVY DEFECTIVE, if A & OK were lighter on the 2nd weigh then A is LIGHT DEFECTIVE…

If B & C don’t balance on the (3rd weigh) then we know one of them is DEFECTIVE so we know A is OK. If B & C were heavier than A & OK (on the 2nd weigh) then we know the defective ball must be HEAVY so which ever is heavier out of B & C is the HEAVY DEFECTIVE ball. If B & C were lighter than A & OK (on the 2nd weigh) then we know the defective ball must be LIGHT so which ever is lighter out of B & C is the LIGHT DEFECTIVE ball.

Puzzle 3: Color.. Color..

This is one of my favorite puzzle. Please don’t put spoilers if you already know the answer.

“If a bear walks one mile south, turns left and walks one mile to the east and then turns left again and walks one mile north and arrives at its original position, what is the color of the bear.”

Please give answer alongwith valid explaination instead of wild guesses.

Replying to Puzzles


To solve the issues of submitting the answers, you can mail them to gurus [dot] comments [at] gmail [dot] com

The steps to be noted are

1. Subject should be the Title of the Post (noting extra, nothing lesser)

2. You can submit your solution as many time as you want, just put a comment about which one you want to be considered.

3. Feel free to ask anything in the comments, any doubts etc, but mail the solutions.

4. For programming contests the same procedure can be followed or you can look for a link like this for the solution.

I hope this works as intended.


Puzzle 2 : Which will take shorter Time?

“If you throw a stone up and considering real world situations like air drag ….. which will take lesser time —- reaching to the top or dropping from the top to where it started…”

Give reasons to support ur answer….

Sol>>> No one has given the correct answer and explanation yet… be the first one to answer it right…

Puzzle 1 : Take a chill pill!

This is one of the Microsoft interview questions, should be easier to answer as writing a code is not required. 🙂

“You have 5 jars of pills. Each pill weighs 10 gram, except for contaminated pills contained in one jar, where each pill weighs 9 gm. Given a scale, how could you tell which jar had the contaminated pills in just one measurement?”

By scale I mean a digital weight measuring machine.


1. Mark the jars with numbers 1, 2, 3, 4, and 5.
2. Take 1 pill from jar 1, take 2 pills from jar 2, take 3 pills from jar 3, take 4 pills from jar 4 and take 5 pills from jar 5.
3. Put all of them on the scale at once and take the measurement.
4. Now, subtract the measurement from 150 ( 1*10 + 2*10 + 3*10 + 4*10 + 5*10)
5. The result will give you the jar number which has contaminated pill.


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