top button
Flag Notify
    Connect to us
      Site Registration

Site Registration

Interviewer has given me 100 marbles(50 white and 50 black) and two empty boxes.............So whats should i have done?

+3 votes
5,808 views

This was asked in an interview of Infosys.
Interviewer has given me 100 marbles(50 white and 50 black) and two empty boxes.
He then told me that he will leave the room and i need to place all the marbles in two boxes.

And When he come back, he will draw a marble from any of the two box and if the marble is black i will be hired.

Also
* No box can be empty.
* All 100 marbles must be placed in one of the two boxes.

So whats should i have done ?

posted Apr 14, 2018 by Pankaj Deshmukh

Share this puzzle
Facebook Share Button Twitter Share Button LinkedIn Share Button

1 Answer

+2 votes

If there are no cheap tricks to this then it becomes a problem of increasing the probability of the interviewer picking a black marble to the maximum.

This can be done by placing 1 black marble on one box and all the rest of the 99 marbles on the 2 box.

The probability if the 2 boxes had equal number of black and white marbles: 0.5×0.5 + 0.5×0.5 = 0.5 = 50%
The probability when 1 box has 1 black marble in one of the boxes and 99 in another: 0.5×1 + 0.5×(49/99) = 0.747474 = 74.7474%.

answer Apr 14, 2018 by Tejas Naik



Similar Puzzles
0 votes

You are a prisoner sentenced to death. The Emperor offers you a chance to live by playing a simple game. He gives you 50 black marbles, 50 white marbles and 2 empty bowls. He then says, "Divide these 100 marbles into these 2 bowls. You can divide them any way you like as long as you use all the marbles. Then I will blindfold you and mix the bowls around. You then can choose one bowl and remove ONE marble. If the marble is WHITE you will live, but if the marble is BLACK... you will die."

How do you divide the marbles up so that you have the greatest probability of choosing a WHITE marble?

0 votes

There are 3 boxes.
One of the Box contains gold
and the other two are empty.
A Printed message contains in each Box.
One of the message is true
and the other two are lies.

The 1st box says "Gold is not here"
The 2nd box says "Gold is not here"
The 3rd box says "Gold is in the second box".
Which box has the Gold?

0 votes

Against your royalty I attack,
Going black to white and white to black
And one by two or two by one,
Until I'm caught or the war is done.
What am i?

...