Finding a Heavier Coin Among Nine

Splitting the coins into three equal groups and comparing two of the groups narrows down which group contains the heavy coin.

Repeat the same three-way split on the remaining group of three coins.

1. 1. First weighing

   Split the nine coins into three groups of three and weigh two of the groups against each other. If they balance, the heavy coin is in the unweighed group; otherwise it is in the heavier group.

2. 2. Second weighing

   Take the identified group of three coins, weigh one coin against another; if they balance the heavy coin is the third, otherwise it is the heavier one on the scale.

Answer: 2