Archive for the 'Puzzles' Category



18
Dec
09

Solutions to WU’s puzzles and riddles : Light Bulb and Switches (medium)

3 Bulbs

I am trying to find all the solutions and put them together at a single place, So feel free to add comments and if you have a solution please do post. Cheers … :)

Here is the puzzles link : http://www.wuriddles.com/

Question : You are in a room with three light switches, each of which controls one of three light bulbs in the next room. Your task is to determine which switch controls which bulb. All lights are initially off, and you can’t see into one room from the other. You are allowed only one chance to enter the room with the light bulbs. How can you determine which light switch goes with which light bulb?

My Solution : For this solution, we need to use some thermal laws ….. :P , sounds funny, but there is no other way. Here we are given 3 bulbs and 3 switches and we can go inside only once. Lets say the Bulbs are named B1,B2,B3 and the corresponding switches are S1,S2,S3. Now what we do is, we switch on the switch S1 and wait for half an hour. After that , we switch on S2 and go inside. After going inside, the bulb which is glowing is B2 obviously.  And now hold the other 2 bulbs. And you can observe that one of the bulb will be hot because it was switched on and kept for half an hour. So that bulb is none other than our S1 and the remaining bulb is S3 … :)

18
Dec
09

Solutions to WU’s puzzles and riddles : Manholes (medium)

Round Manholes

I am trying to find all the solutions and put them together at a single place, So feel free to add comments and if you have a solution please do post. Cheers … :)

Here is the puzzles link : http://www.wuriddles.com/

Question : Why are manholes round?

Note: This is a famous Microsoft question. Yet amusingly, the Microsoft campus uses square manholes.

My Solution : I guess there are 2 basic reasons for this. The first one is that, the cover cant get inside the manhole whatever we do. But a square manhole can pass through the man hole by putting it diagonally. And the second one is carrying it is very easy. We can roll over the cover from one place to other easily, where as in the square manhole, its not possible……. :)

18
Dec
09

Solutions to WU’s puzzles and riddles : Ghetto Encryption 2 (medium)

Ghetto's Puzzle 2

I am trying to find all the solutions and put them together at a single place, So feel free to add comments and if you have a solution please do post . Cheers … :)

Here is the puzzles link : http://www.wuriddles.com/

Question : Three coworkers would like to know their average salary. However, they are self-conscious and don’t want to tell each other their own salaries, for fear of either being ridiculed or getting their houses robbed. How can they find their average salary, without disclosing their own salaries?

My Solution : Let the 3 idiots be A,B and C. First A will add some ‘x’ amount to his salary and give that final value to B. Will will add his salary plus some ‘y’ to the sum which A has given and then give the total sum to C. C will add some ‘z’ to his salary and then adds the total sum to A’s and B’s and passes back to A.

Now A will subtract ‘x’ and pass it on to B. B will subtract ‘y’ and will pass it on to C. C will subtract ‘z’ to get the sum of the salaries of A,B and C …:)

18
Dec
09

Solutions to WU’s puzzles and riddles : Ghetto Encryption 1 (medium)

Ghetto Puzzle

I am trying to find all the solutions and put them together at a single place, So feel free to add comments and if you have a solution please do post . Cheers … :)

Here is the puzzles link : http://www.wuriddles.com/

Question : You want to send a valuable object to a friend securely. You have a box which can be fitted with multiple locks, and you have several locks and their corresponding keys. However, your friend does not have any keys to your locks, and if you send a key in an unlocked box, the key could be copied en route. How can you send the object securely?

Alternative, more precise phrasing: Andy and Grant are staying in different rooms in the same hotel. Andy needs to give a gold pendant to Grant, but spies are trying to assassinate Andy and Grant so neither of them can leave their room. The only way they can transfer objects is by using the bellhops. Both Andy and Grant have a safe with a large clasp that can be secured with a padlock. Both Andy and Grant have a padlock and a corresponding key. (So 1 gold pendant, 2 safes, 2 padlocks, and 2 keys.) But the bellhops are thieves. Anything that is not padlocked in the safe will be stolen by the bellhops – including any unlocked padlocks, the keys or the pendant. How can Andy transfer the gold pendant to Grant without it being stolen? (where both sides have encryption capability, and where unsecured items are taken away rather than just copied?)

My Solution : Andy will put the gold pendent in the box and then locks with Andy’s lock and passes the box to Grant. Now Grant will put on his lock and then passes back to Andy. Now Andy removes his lock and passes back to Grant and its done ….. :P So simple, right …. :P

17
Dec
09

Solutions to WU’s puzzles and riddles : Birthday Twins (hard)

BIRTHDAY TWINS

I am trying to find all the solutions and put them together at a single place, So feel free to add comments and if you have a solution please do post. Cheers … :)

Here is the puzzles link : http://www.wuriddles.com/

Question : Sheila and He-Man are twins; Sheila is the OLDER twin. Assume they were born immediately after each other, an infinitesimally small – but nonzero – amount of time apart. During one year in the course of their lives, Sheila celebrates her birthday two days AFTER He-Man does. How is this possible?

Bonus: What is the maximum amount of time by which Sheila and He-Man can be apart in their birthday celebrations during the same year? I think it’s more than two days.

Note: For both Sheila and He-Man, these birthday celebrations happen on the actual birthday date — it cannot be a celebration that occurs at a date earlier or later than the actual birthday date for whatever reasons of convenience. Also, the solution has nothing to do with the theory of relativity or any other over complicated nonsense like that.

My Solution : For this problem we need to consider the case of time zones. The mother must have been travelling in a boat or i a plane and must have crossed the time zone after the first birth. The first one was born on 1st of March and the the mother crossed the time zone and its still 28th of February in the other time zone and the second one was born. Hence the elder one was born logically after the second twin. So in a particular leap year, the second twin will celebrate his birthday on 28th February and 2 days later his elder sister will celebrate her birthday. …. :)

17
Dec
09

Solutions to WU’s puzzles and riddles : Force Field Detainment (medium)

FORCEFIELD DETAINMENT

I am trying to find all the solutions and put them together at a single place, So feel free to add comments and if you have a solution please do post . Cheers … :)

Here is the puzzles link : http://www.wuriddles.com/

Question :  A group of prisoners are trapped in a forcefield. These prisoners are perfectly brave, meaning that they would attempt an escape on any positive probability of success. The prisoners are monitored by a guard who has only one bullet in his gun, but who also has perfect marksmanship skills (he never misses). A maintenance technician needs to tune up the forcefield generator, and so for one second, the forcefield is released. How can the guard still keep all the prisoners detained?

My Solution : The guard says that, who ever comes out of the field first, i will shoot that guy. Now since all the prisoners know that the guard is very skilled and cant miss the shot, no one dares to go first.

16
Dec
09

Solutions to WU’s puzzles and riddles : Where’s the Father (medium)

Where is the Father

I am trying to find all the solutions and put them together at a single place, So feel free to add comments and if you have a solution please do post. Cheers … :)

Here is the puzzles link : http://www.wuriddles.com/


Question : The mother is 21 years older than the child. In 6 years from now, the mother will be 5 times as old as the child. Question: Where’s the father?

My Solution : If you calculate the value of the age of the baby, you will get – 3/4 = – 0.75 = 9 months

This is derived from this equation :

27+x = 5 (x+6)      =>  27+x = 5x+30  => 4x = -3  => x = -3/4 = 9 months before the baby was born.

Hence the Father is with the Mother




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