1. There are two incense sticks distributed unevenly. The time it takes for the incense to burn out is one hour. How can you determine a period of 15 minutes?

Answer: Light two incense at the same time. The first incense is lit at both ends, and the other incense is burned at only one end. When the first incense is burned out (this is the total length of the incense burned out) 3/4), light the other end of the second incense, the time from burning to extinguishing the other end is 15 minutes!

2. A manager has three daughters. The sum of the ages of the three daughters is equal to 13. The sum of the ages of the three daughters is equal to the manager’s own age. A subordinate already knows the manager’s age, but still cannot Determine the ages of the manager's three daughters. At this time, the manager said that only one daughter has black hair. Then the subordinate knew the ages of the manager's three daughters. What are the ages of your three daughters? Why?

Answer: The ages of the three girls should be 2, 2, and 9. Because there is only one child with black hair, that is, she is the only one who has grown up, and the other two are still in childhood, that is, less than 3 years old, with light hair. Combined with this, the age of the manager should be at least greater than 25.

3. Three people went to stay in a hotel and stayed in three rooms. Each room cost $10, so they paid the boss $30 one day. The next day, the boss thought the three rooms only cost $25. Yuan was enough, so I asked the boy to return $5 to the three guests. Who knew that the boy was greedy, so he only returned $1 to each person, and secretly took $2 for himself. In this way, the three guests each spent nine yuan, so the three I spent $27 per person, plus my little brother ate away $2, the total was $29. But when the three of them paid $30 a ***, what about the remaining $1?

Answer: The 30 yuan paid per day includes 27 yuan (25 yuan for the boss + 2 yuan embezzled by the younger brother) and 1 yuan returned to each person (***3 yuan). Take 27 and 2 yuan Adding them up is purely confusing.

4. There are two blind men. They each bought two pairs of black socks and two pairs of white socks. The eight pairs of socks were made of the same fabric and size, and each pair of socks had a piece of trademark paper. Connected. Two blind men accidentally mixed up eight pairs of socks. How can each of them retrieve two pairs of black socks and two pairs of white socks?

Answer: Open each pair of socks, each person takes one pair, there are no left and right socks, and finally get two pairs of black socks and two pairs of white socks.

5. A train leaves Los Angeles and goes straight to New York at a speed of 15 kilometers per hour, and another train leaves New York and goes to Los Angeles at a speed of 20 kilometers per hour. If a bird starts from Los Angeles at the same time as two trains at a speed of 30 kilometers per hour, encounters another car and returns, flying back and forth on the two trains until the two trains meet, what will this bird do? How far did the bird fly?

Answer: Convert the bird’s flight distance into time. Suppose the distance between Los Angeles and New York is a, the time when the two trains meet is a/(15 20)=a/25, and the bird’s flight speed is 30, then the bird’s flight distance is a/25*30=6 /5a.

6. You have two jars, 50 red marbles and 50 blue marbles. Randomly select a jar and randomly select a marble and put it into the jar. How to give red marbles? Pinball’s greatest chance of selection? In your plan, what is the exact probability of getting a red ball?

Answer: Put a red ball in one jar, 49 red balls and 50 blue balls in another jar. The probability is close to 75.

This is the maximum probability that can be achieved. .

Actually, only 1 can be placed in a jar. For each person wearing black, he can see N-1 black hats, and thus assumes that he is white. But after waiting for N-1 times and no one hits him, every black person will know that he is also black. So when you turn off the lights for the Nth time, N people will hit you.

12. There are two rings with radii of 1 and 2 respectively. The small circle goes around the circumference of the large circle inside the large circle. How many times does the small circle rotate by itself? If it is outside the big circle, how many times will the small circle rotate by itself?

Answer: No matter inside or outside, the small circle rotates twice. The distance experienced by the small circle and the big circle is equal.

13. A bottle of soda costs 1 yuan. After drinking, two empty bottles are exchanged for one bottle of soda. Question: You have 20 yuan. How many bottles of soda can you drink at most?

Answer: 39 bottles, starting from the second bottle, which is equivalent to buying 2 bottles for 1 yuan.