1. A person bought a chicken for 8 yuan and sold it for 9 yuan. Then he thought it was not worthwhile, 10 yuan bought it back and sold it to another person for 1 1 yuan. Ask him how much money he earned.

Answer: 2 yuan.

2. Suppose there is a pond with infinite water. At present, there are two empty kettles with a capacity of 5 liters and 6 liters respectively. The problem is how to get 3 liters of water from the pond with only these two kettles.

Answer: Fill it with a 5-liter pot and pour it into a 6-liter pot.

Pour the 5-liter pot into the 6-liter pot until the 6-liter pot is full. At this point, there are 4 liters of water left in the 5 liter pot.

Pour all the water out of the 6-liter pot, and pour the remaining 4 liters of water from the 5-liter pot into the 6-liter pot. At this time, there are only 4 liters of water in the 6-liter pot.

Fill the 5-liter pot again and pour into the 6-liter pot until the 6-liter pot is full. At this time, there are only 3 liters of water left in the 5-liter pot.

3. A farmer took three rabbits to the market to sell. Each rabbit weighs about three or four kilograms, but the farmer's scale can only weigh more than five kilograms. He asked him what he called it.