There are 80 coins, among them one coin weighs less compared
to other. You are given a physical balance to weigh. In how
many wieghings the odd coin can be found.

Answer Posted / antariksh

divide coins into 3 groups,27,27,26.
1st weighing : first compare the weight of 27 and 27.If
they are equal then the third collection of 28 coins
contains the faulty coin else the lesser weighing collection
of 27 coins has the faulty coin.
2nd weighing : then divide the 27 coins into 9,9,9 of three
groups ,again compare the two 9's of them.if they are equal
then the third collection of 9 coins contains the faulty
coin else the lesser weighing collection of 9 coins has the
faulty coin.
3rd weighing : then divide the coin in 3 groups of 3.again
compare the two 3's of them.if they are equal then the third
collection of 3 coins contains the faulty coin else the
lesser weighing collection of 3 coins has the faulty coin.
4th weighing :now compare the two coins of them.if they are
equal then the third coin is the faulty coin else the lesser
weighing coin is the faulty coin.

Is This Answer Correct ?    58 Yes 14 No



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