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### Cool Interview Puzzles With Answers

Cool Interview Puzzles With Answers 1 : Hardest Balance Logic Puzzle
Difficulty ★★★★★        Popularity ★★★★★

You are given a set of scales and 12 marbles. The scales are of the old balance variety. That is, a small dish hangs from each end of a rod that is balanced in the middle. The device enables you to conclude either that the contents of the dishes weigh the same or that the dish that falls lower has heavier contents than the other.
The 12 marbles appear to be identical. In fact, 11 of them are identical, and one is of a different weight. Your task is to identify the unusual marble and discard it. You are allowed to use the scales three times if you wish, but no more.

Note that the unusual marble may be heavier or lighter than the others. You are asked to both identify it and determine whether it is heavy or light.

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Cool Interview Puzzles With Answers 2 : Hard Measuring Water Riddle
Difficulty ★★★★★        Popularity ★★★★★

You have two buckets of 11liter and 6liter.
How can you measure exactly 8liter ?
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Cool Interview Puzzles With Answers 3 : Challenging Puzzle
Difficulty ★★★★☆        Popularity ★★★★★

Outside a room there are three light switches. One of switch is connected to a light bulb inside the room.
Each of the three switches can be either 'ON' or 'OFF'.

You are allowed to set each switch the way you want it and then enter the room(note: you can enter the room only once)

Your task is to then determine which switch controls the bulb ??
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Cool Interview Puzzles With Answers 4 : River Riddle
Difficulty ★★★★☆        Popularity ★★★★★

Four people need to cross a dark river at night.They have only one torch and the river is too risky to cross without the tourch. if all people cross simultanoesly then torch light wont be sufficient.Speed of each person of crossing the river is different.cross time for each person is 1 min, 2 mins, 7 mins and 10 mins. What is the shortest time needed for all four of them to cross the river ?
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Cool Interview Puzzles With Answers 5 : Logic Interview Question
Difficulty ★★★★☆        Popularity ★★★★★

The first box has two white balls. The second box has two black balls. The third box has a white and a black ball.

Boxes are labeled but all labels are wrong!

You are allowed to open one box, pick one ball at random, see its color and put it back into the box, without seeing the color of the other ball.

How many such operations are necessary to correctly label the boxes?
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Cool Interview Puzzles With Answers 6 : Oracle Probability Interview Question
Difficulty ★★★★☆        Popularity ★★★★★

What is the probability of choosing the correct answer at random from the options below.

a) 1/4
b) 1/2
c) 1
d) 1/4
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Cool Interview Puzzles With Answers 7 : Classic Logical Interview Puzzle
Difficulty ★★★☆☆        Popularity ★★★★★

I have two rectangular wires.
Both of them have property that when i light the fire from one end , it will take 60 minutes to get completely burn.
However they do not burn at consistent speed (i.e it might be possible 1st 20% burn in 50 minutes and 80% can burn in 10 minutes).

So how could i measure 45 minutes ?

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Cool Interview Puzzles With Answers 8 : Qualcomm Logic Interview Puzzle
Difficulty ★★★★☆        Popularity ★★★★☆

A convention is held where all the big logicians are summoned. The master places a band on everyone's forehead. Now all of them can see others' bands but can't see his own. Then they are told that there are different colors of bands. All the logicians sit in circle and they are further explained that a bell will ring at regular intervals. The moment when a logician knew the color of band on his forehead, he will leave at the next bell. If anyone leaves at the wrong bell, he will be disqualified.

The master assures the logicians that the puzzle will not be impossible for anyone of them. How will the logicians manage ?

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Cool Interview Puzzles With Answers 9 : Knockout Tournament Matches Puzzle
Difficulty ★★★☆☆        Popularity ★★★★☆

A chess tournament is taking place on knock-out terms (the one who loses the match is out of the game).
(a) If 15 matches are played in total, how many players participated?
(b) If 50 players took part in the tournament, how many matches were played?
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Cool Interview Puzzles With Answers 10 : Marbles Puzzle
Difficulty ★★☆☆☆        Popularity ★★★★☆

There is a box full of marbles,
all but two are blue,
all but two are green,
and all but two are red.

How many marbles are in the box ?
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