# Puzzle Set – 2

Puzzle Set 1

1. I offer to play a card game with you using a normal deck of 52 cards.  the rules of the game are that we will turn over two cards at a time.  if the cards are both black, they go into my pile.  if they are both red, they go into your pile.  if there is one red and one black, they go into the discard pile. We repeat the two card flipping until we’ve gone through all 52 cards.  whoever has more cards in their pile at the end wins.  i win if there is a tie.  if you win, i pay you a dollar.  how much would you pay to play this game? Solution 1 and 2.
2. Four people need to cross a rickety bridge at night. Unfortunately, they have only one torch and the bridge is too dangerous to cross without one. The bridge is only strong enough to support two people at a time. Not all people take the same time to cross the bridge. Times for each person:  1 min, 2 mins, 7 mins and 10 mins. What is the shortest time needed for all four of them to cross the bridge?
3. Mr. Black, Mr. Gray, and Mr. White are fighting in a truel. They each get a gun and take turns shooting at each other until only one person is left. Mr. Black, who hits his shot 1/3 of the time, gets to shoot first. Mr. Gray, who hits his shot 2/3 of the time, gets to shoot next, assuming he is still alive. Mr. White, who hits his shot all the time, shoots next, assuming he is also alive. The cycle repeats. If you are Mr. Black, where should you shoot first for the highest chance of survival?
4. Set of few problem in a video.
5. Defective Ball –  You have 10 boxes of balls (each ball weighing exactly10 gm) with one box with defective balls (each one of the defective balls weigh 9 gm). You are given an electronic weighing machine and only one chance at it. How will find out which box has the defective balls?
6. Tic-tac toe  http://quiz.geeksforgeeks.org/puzzle-80-tic-tac-toe/
http://quiz.geeksforgeeks.org/puzzle-38-tic-tac-toe-puzzle/
7. There was a prison consisting of 1000 cells numbered from 1 to 1000.
Each cell can be marked with ‘+’ or ‘-‘sign. Initially, all cells were marked with ‘-‘ sign.
From days 1 to 1000,the jailor toggles marks on the cell from + to – or vice versa.
On the i-th day ,the signs on cells that are multiples of i get toggled.
Now in the process of verification on 1001-th day, all cells marked with + signs are opened.
Can you identify the cell numbers with ‘+’ sign?
Answer – This concept is important.
8. http://quiz.geeksforgeeks.org/puzzle-77-the-better-choice/ – based on geometrical progression.
9. ** Prisoner’s Hat
10. You have 15 Rs with you. You go to a shop and shopkeeper tells you price as 1 Rs per chocolate. He also tells you that you can get a chocolate in return of 3 wrappers. How many maximum chocolates you can eat?
11. [26 May 2017] There are 3 ants sitting on three corners of a triangle. All ants randomly pick a direction and start moving along edge of the triangle. What is the probability that any two ants collide?
12. [27 May 2017] How can you represent days of month using two 6 sided dice
13. [28 May 2017]There is an 8 by 8 chessboard in which two diagonally opposite corners have been cut off.You are given 31 dominos, and a single domino can cover exactly two squares. Can you use the 31 dominos to cover the entire board?
14. [29 May 2017] Three Employees want to know average of their salaries. They are not allowed to share their individual salaries.
15. [30 May 2017] If you have seven white socks and nine black socks in a drawer, how many socks do you have to pull out blindly to ensure that you have a matching pair?  Pigeonhole Principle . Link
16. [31 May 2017]