Short Bytes: NSA regularly puts on brain-teasers on its website every month. These NSA puzzles are created by the intelligent people who work there. Let’s see if you can find the solution to these questions.The National Security Agency, which got hacked recently, of the United States has been there for years. Most of the world came to knew about its existence in 2013 when Edward Snowden pulled the curtains off the surveillance activities conducted by them.
Keep their spying habits apart, most of us don’t know that NSA is very regular, since the last few months, in publishing a monthly puzzle for the common public under the title Puzzle Periodicals. Last year, they published puzzles between July and October. These brain-twisters, enough to blow your mind, are made by intelligent minds working at NSA. They are designed to test your logical, mathematical and other mental abilities.
This is the puzzle periodical for the month of August 2016 submitted by Ben H., who is a systems engineer at NSA:
At a work picnic, Todd announces a challenge to his coworkers. Bruce and Ava are selected to play first. Todd places $100 on a table and explains the game. Bruce and Ava will each draw a random card from a standard 52-card deck. Each will hold that card to his/her forehead for the other person to see, but neither can see his/her own card. The players may not communicate in any way. Bruce and Ava will each write down a guess for the color of his/her own card, i.e. red or black. If either one of them guesses correctly, they both win $50. If they are both incorrect, they lose. He gives Bruce and Ava five minutes to devise a strategy beforehand by which they can guarantee that they each walk away with the $50.
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Bruce and Ava complete their game and Todd announces the second level of the game. He places $200 on the table. He tells four of his coworkers — Emily, Charles, Doug and Fran—that they will play the same game, except this time guessing the suit of their own card, i.e. clubs, hearts, diamonds or spades. Again, Todd has the four players draw cards and place them on their foreheads so that each player can see the other three players’ cards, but not his/her own. Each player writes down a guess for the suit of his/her own card. If at least one of them guesses correctly, they each win $50. There is no communication while the game is in progress, but they have five minutes to devise a strategy beforehand by which they can be guaranteed to walk away with $50 each.
For each level of play – 2 players or 4 players– how can the players ensure that someone in the group always guesses correctly?
Check out more of such brain teasers at the NSA’s 2016 Puzzle Periodical.
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