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Q17. Alok and Bhanu play the following coins in a circle game. 99 coins are arranged in a circle with each coin touching two other coin. Two of the coins are special and the rest are ordinary. Alok starts and the players take turns removing an ordinary coin of their choice from the circle and bringing the other coins closer until they again form a (smaller) circle. The goal is to bring the special coins adjacent to each other and the first player to do so wins the game. Initially the special coins are separated by two ordinary coins O1 and O2. Which of the following is true?

a) In order to win, Alok should remove O1 on his first turn.
b) In order to win, Alok should remove one of the coins different from O1 and O2 on his first turn.
c) In order to win, Alok should remove O2 on his first turn.
d) Alok has no winning strategy.

Profile image of sajal saxena
14 Years agoGrade 12th Pass
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1 Answer

Profile image of Ashwin Muralidharan IIT Madras
14 Years ago

Hi Sajal,

 

This more so seems like a CAT question, than an IIT-JEE question.

 

The logic here is that, C1/C2 should be the last of the coins to remove.

Leaving the two spl coins and O1, O2 there are 95 coins left. Alok and Bhanu both shouldn't remove one of O1/O2 in the firs place until all other ordinary coins are removed, as their objective is to win.

 

So out of the remaining 95 coins, if Alok starts, by removing the 1st coin and then Bhanu removing the 2nd coin and so on.... finally Alok would remove the 95th coin, now leaving no choice for Bhanu, but to remove one of O1/O2. Then Alok removes the only ordinary coin left, and would win the game.

 

And hence the option B.

 

Hope that helps.

 

All the best,

Regards,

Ashwin (IIT Madras).