You have 9 balls, one of which is slightly heavier or lighter. How many times do you need to weigh them to find the heavier or lighter one?
Q1. You have 9 balls, one of which is slightly heavier or lighter. How many times do you need to weigh them to find the heavier or lighter one?
Answer: 3
Explanation: Divide the balls into 3 groups: 3, 3, and 3. Weigh 3 against 3. If balanced, the different ball is in the remaining 3. Weigh 1 against 1 from the group of 3. If still balanced, the remaining is the different one.