coins

[Jaswinder24]

There are 9 coins, one of which is a fake. This fake coin is lighter as compared to other coins. Use a balance to weigh them in the minimum number of steps and find the fake coin.

[dr john]

Two weighings:

Divide the coins into three sets of 3, choose two sets and weigh them against each other. If they weigh the same, the fake is in the third set; if not it's in the lighter set.

Take the three coins containing the fake, and weigh two of them against each other. If one is lighter it's the fake; if they weigh the same the third one is.