Question :
1. You have 9 coins with same size.
2. Among those 1 Coin has less weight.
3. You have Weighting scale to find the Odd Coin.
In How many minimum number of times can you use Weighting scale to find the odd coin.?

Answer is 2.
Step1: Take 3 coins in one side of scale and 3 more coins in another side. and judge the scale 1. if both groups are equal then then take the remaining 3 coins to proceed Step2. 2. Otherwise take the group which has less weight to proceed Step2. Step2: Now you have 3 coins. take one coin in one side and one more coin in another side and judge the scale. 1. if both are equal then then the 3rd coin is the odd one. 2. Other wise the coin which has less weight is the odd one.