Solution of Bridge crossing Riddle

Solution:
-> 1. + 2. - 2 min
<- 1. - 1 min
-> 3. + 4. - 9 min
<- 2. - 2 min
-> 1. + 2. - 2 min

Total - 16 min
note:
-> forward direction
<- Reverse direction

POST YOUR OPINION IF YOU HAVE BETTER SOLUTION

Bridge crossing Riddle

Question:
There are four people at the end of bridge. They take following time to cross the bridge:
1st: 1 min
2nd: 2 min
3rd: 7 min
4th: 9 min

Condition: 
1. They have only one torch and they can't cross bridge without torch.
2. and only 2 person can cross bridge at a time.

Solution of Burn the rope....good puzzle

Solution:
Take 2 ropes R1, R2. Light R1 at both ends and R2 at one end. When R1 is completely burned (30 minutes have passed), light R2 at the other end. When R2 is completely burned 45 minutes have passed.

POST YOUR OPINION IF YOU HAVE BETTER SOLUTION

Burn the rope....good puzzle

Question:
there are unlimited ropes of same length and if we burn them it will take 1 hour.
How to measure 45 mins?

Solution of 100 door puzzle....microsoft interview puzzle

Solution:

This problem is designed to seem overwhelming. You don’t have time to draw a diagram of 100 lockers and count 100 passes through them. Even if you did, solving the problem that way wouldn’t illustrate any skill or intuition, so there must be some trick that can be used to determine how many doors will be open. You just have to figure out what that trick is.

It’s unlikely that you’re going to be able to intuit the solution to this problem by just staring at it. What can you do? Although it’s not practical to solve the entire problem by brute force, solving a few lockers in this manner is reasonable. Perhaps you’ll notice some patterns you can apply to the larger problem.
Start by choosing an arbitrary locker, 12, and determining whether it will end open or closed. On which passes will you toggle locker 12? Obviously on the first pass, when you toggle every locker, and on the twelfth pass when you start with 12. You don’t need to consider any pass after 12 because those will all start farther down the hall. This leaves passes 2 through 11. You can count these out: 2, 4, 6, 8, 10, 12 (you toggle on pass 2); 3, 6, 9, 12 (on 3); 4, 8, 12 (on 4); 5, 10, 15 (not on 5); 6, 12 (on 6); 7, 14 (not on 7), and so on. Somewhere in the middle of this process, you will probably notice that you toggle locker 12 only when the number of the pass you’re on is a factor of 12. If you think about this, it makes sense: When counting by n, you hit 12 only when some integer number of n’s add to 12, which is another way of saying that n is a factor of 12. Though it seems simple in retrospect, this probably wasn’t obvious before you worked out an example.

Solution of 2 Egg Problem: Google Interview Puzzle

Solution:

Drop the first egg from 50.If it breaks you can try the same approach for a 50-storey building (1 to 49) and try it from 25th floor. If it did not break try at 75th floor. And use linear search with the remaining portion of storey we need to test. For example if the first egg breaks at 50 we need to try all possibilities from 1 to 49.

Now this looks a feasible solution. In computer student's jargon do a binary search with first egg and linear search with the second one. Best case is log (100) and worst is 50.

Solution of Village of demons & sleeping man puzzle....tricky puzzle

Solution:

1 demon 1 human
demon eat human.
2 demon 1 human
nothing happens.

3 demon 1 human
one demon eat the human.
Explanation:
if there are odd number of eaters and one sleeping target, one of the eater(demon) will eat the target(sleeping demon/man).

Village of demons & sleeping man puzzle....tricky puzzle

Question:

given a village with demons and a sleeping man, The man is always sleeping ,never wakes up. Now a demon can eat the sleeping man , but after that
he will fall asleep , any demon can eat another sleeping demon.

If demons are very smart and would always choose to stay alive than to eat the man and risk their lives.
so if initially there are 65 demons and 1 sleeping man .. what would happen in the village ??

Find bad apples from boxes in 1 attempt...!!!

Question:
There are 10 boxes of apples. Each apple in the boxes weights 1 pound, except that one of the boxes contains bad apples, which weights 0.9 pound each. You are given a digital weight (not a scale), and you can take apples out of the boxes. what is the minimum time of weighs to find out which box has bad apples?

Solution:

it's simple:
take 1 apple from box 1, 2 apples from box 2 ... 10 apples from box 10

Google letter/number series puzzle

Puzzle:

Fill in the blanks:

--   --  --  H  I   K  L   M   N  T
     --   --  --  G  J  O  P  Q   R  S

Answer:
hint:Characters in the top row are written with straight lines, whereas those in the bottom row are written with curved lines.

1) This pattern perfectly fits with the first 6 characters.
A E F
B C D

17 min bridge crossing puzzle

Puzzle:
There are four people who want to cross a bridge; they all begin on the same side. You have 17 minutes to get them all across to the other side. It is night, and they have one flashlight. A maximum of two people can cross the bridge at one time. Any party that crosses, either one or two people, must have the flashlight with them.
The flashlight must be walked back and forth; it cannot be thrown, for example. Person 1 takes 1 minute to cross the bridge, person 2 takes 2 minutes, person 3 takes 5 minutes, and person 4 takes 10 minutes. A pair must walk together at the rate of the slower person’s pace. For example, if person 1 and person 4 walk across first, 10 minutes have elapsed when they get to the other side of the bridge. If person 4 returns the flashlight, a total of 20 minutes have passed and you have failed the mission.

9 card puzzle

Question:
9 cards are there. u have to arrange them in a 3*3 matrix.
cards are of 4 colors.they are red,yellow,blue,green.
conditions for arrangement: one red card must be in first row
or second row.2 green cards should be in 3rd column.Yellow
cards must be in the 3 corners only. Two blue cards must be in
the 2nd row. Atleast one green card in each row.

100 door puzzle....microsoft interview puzzle

Question:
Lets say you have a room with 100 doors in it. Initially, all of these doors are open. You have 100 people that will be entering the room. The 1st person toggles every door, 2nd person toggles every other door, 3rd toggles every 3rd door, ... , nth person toggles every nth door. How would you determine the state of all 100 doors after all 100 people have entered the room?

1000 barrels Puzzle

Question:
A king is about to give a party in 24 hours. For the party they have arranged drinks which will be served through 1000 barrels. Out of jealousy , some one near to king has poisoned one of the barrels. The poison is so strong that even a drop can kill a person. But results are not immediate. A person may die from 13 to 20 hrs. Now king has a duty of finding that barrel. He has 24 hours with him. And he has unlimited prisoners on which the drinks can be tested. Find out the maximum prisoners he would need to find out that barrel.

2 dice puzzle

Question:
You are given 2 dice. Both are fair. One of the dice has no numbers printed on it. You have to label the unmarked dice such that when both the dice are thrown, the sum on the faces is evenly distributed between 1 and 12.

count the number of students in a classroom in quickest way

Question:

How will you count the number of students in a classroom in quickest possible manner.

Solution:
Ask the class to stand up and make pairs, if one student is left out write '1' else write 0. tell the left out student to sit down and ask one person in each group to sit down. Repeat the process and append '1' or '0' to your number, until no student is left standing. You will get the binary representation of the number of students in reverse order.

Obtain 4 litre from 5 & 3 litre jar

Question:
There are 2 jars 5 lit and 3 lit capacity
measure 4 lit using them

Find top 5 horse from 25 horses

Question:

how to find top 5 horses from 25 if there are only 5 lanes.In min no. of races?

3black and 2 white cap tricky puzzle

Question:
3 black caps and 2 white caps
randomly 3 caps are chosen and A,B,C are made to wear
they are standing in que and A can see B nC , B can only see C and C cant see anyone
A is asked which cap are you wearing? Ans from A was he dont knw
B was asked which cap is he wearing? B answered I dont know
But when asked C , he gave the correct answer
The question was...which color cap was C wearing?

Red Marbles and Blue Marbles puzzle...goggle puzzle

Problem:

you have two jars, 50 red marbles, 50 blue marbles. you need to place all the marbles into the jars such that when you blindly pick one marble out of one jar, you maximize the chances that it will be red. (when picking, you’ll first randomly pick a jar, and then randomly pick a marble out of that jar) you can arrange the marbles however you like, but each marble must be in a jar.