Three questions during the interview ......

1. There are two kettles, one can hold 5 liters of water, and the other can hold 3 liters of water. How can I hold 4 liters of water in a 5 litre kettle ??
A: First fill the three-litre water bottle with water, pour the water into the five-litre water bottle, then fill the three-litre water bottle with water, and then pour it into the five-litre water bottle, at this time, the 5-litre water bottle is full, and 1 litre of water is left in the 3-litre water bottle. Drop the water in the 5 litre water bottle, then pour the 1 litre water in the 3 litre water bottle into the 5 litre water bottle, and then fill the water in the 3 litre water bottle, in the 5-litre water bottle, you can use the 5-litre water bottle to hold the 4-litre water.
2. Suppose you have eight balls, one of which is slightly heavier. You have a balance that can be called weight. How many times does it take to find this heavy ball ??
A: At least two times can be used to find the heavier ball.
Step 1: Put three at one side and observe which side is heavy (123-456 ratio). There are two situations
I. The two sides are equally heavy. At this time, we can directly compare the remaining two balls (7 to 8 ratio). Whoever chooses the same one is the same.
2: one side is a little heavier (assuming 123 light). At this time, two balls are taken from the heavy side for comparison (1-2 ratio ).
I. Same weight, that is, the ball is not as light as the ball (3)
2. There is a weight, that is, it (1 or 2)
3. Each bottle of soda costs 1 RMB. You can change one bottle of soda for two empty water bottles. How many bottles of soda can you drink for 20 RMB?
A: You can drink up to 39 bottles.