2. A manager has three daughters, and their ages add up to 13, which is equal to the manager's own age. A subordinate knows the manager's age, but still can't determine the age of the manager's three daughters. At this time, the manager said that only one daughter's hair was black, and then the subordinates knew the age of the manager's three daughters. What are the ages of the three daughters? Why?
3. Three people went to a hotel and stayed in three rooms. The price of each room is $65,438+00, so they pay the boss $30.
The next day, the boss thought that $25 was only enough for three rooms, so he asked his brother to return $5 to three guests.
Who knows, my younger brother was greedy, and only returned 1 USD to everyone, and secretly took $2, which was equivalent to nine dollars for each of the three guests.
So three people spent 27 * * *, and the younger brother left 2 dollars, so the total was 29 dollars. But at the beginning, the three of them paid 30 dollars, so 1 dollar?
4. There are two blind people. They all bought two pairs of black socks and two pairs of white socks. Eight pairs of socks are made of the same cloth and the same size.
Each pair of socks is affixed with trademark paper. Two blind people accidentally mixed up eight pairs of socks. How can each of them get back two pairs of black socks and two pairs of white socks?
5. One train leaves Los Angeles for new york at a speed of 15km/h, and the other train leaves new york for Los Angeles at a speed of 20km/h ... If a bird starts from two trains at a speed of 30 km/h, meets another train and returns, and flies back and forth in turn until the two trains meet, how long does it take for the bird to fly?
6. You have two cans, 50 red marbles and 50 blue marbles. Choose a jar at random and put a marble in the jar at random. How can you give red marbles the best chance? What is the exact probability of getting the red ball in your plan?
7. You have four jars containing pills. Each pill has a certain weight. The contaminated pill is the uncontaminated weight+1. You only weigh it once. How do you know which jar is polluted?
8. You have a bucket of jelly, including yellow, green and red. Close your eyes and grab two jellies of the same color. How many can you catch to make sure you have two jellies of the same color?
9. For a batch of lights numbered 1 ~ 100, all the switches are turned up (turned on), and the following operations are done: always turn the switches in the opposite direction once in multiples of 1; A multiple of 2 toggles the switch in the opposite direction again; A multiple of 3 turns the switch in the opposite direction again ... Q: Finally, the number of lights in the off state.
10. Imagine you are in front of the mirror. Excuse me, why can the image in the mirror be upside down, but not upside down?
1 1, a group of people are dancing, everyone is wearing a hat. There are only two kinds of hats, black and white, and there is at least one kind of black. Everyone can see the color of other people's hats, but not their own. The host first shows you what hats others are wearing, and then turns off the lights. If someone thinks he is wearing a black hat, he will slap himself in the face. The first time I turned off the lights, there was no sound. So I turned on the light again and everyone watched it again. When I turned off the light, it was still silent. I didn't get a slap in the face until I turned off the light for the third time. How many people are wearing black hats?
12, two rings with radii of 1 and 2 respectively. The small circle goes around the big circle. How many times does the small circle turn by itself? If it is outside the big circle, how many times does the small circle turn by itself?
13, 1 Yuan, one bottle of soda, two empty bottles for one bottle. Q: You have 20 yuan money, how many bottles of soda can you drink at most?
Answer: 1. Light two incense sticks at the same time, one at one end, one at both ends and one for half an hour. Then, light the other end of the unfinished rod, and it takes 15 minutes from this time until the second rod comes out.
3. Confuse people and make mistakes.
"So three people spent $27, and my brother left $2, so the total was $29." This sentence is wrong. What you give and what you take should be subtracted, not added. Three people spend 27, the younger brother gets 2, and the remaining 25 is with the boss. This is normal logic.
5. Let the distance between the two places be S, the time when two cars meet is T .. The flying distance of birds is S'.
S = 35*T
S`= 30*T
S`= 6/7*S .
(The flying distance is directly proportional to the distance between the two places, and the distance between the two places has no actual value, so it can only be replaced by S.. )
7. You have four jars containing pills. Each pill has a certain weight. The contaminated pill is the uncontaminated weight+1. You only weigh it once. How do you know which jar is polluted?
{Mark the four bottles with one, two, three and four respectively, then take out the pills with the same number from each bottle, and then ask how much your 10 pill is heavier than the standard 10 pill, indicating that there is something wrong with the bottle number. }
10. Imagine you are in front of the mirror. Excuse me, why can the image in the mirror be upside down, but not upside down?
{Because people's eyes are left and right, not up and down}
13, 1 Yuan, one bottle of soda, two empty bottles for one bottle. Q: You have 20 yuan money, how many bottles of soda can you drink at most?
{40 bottles}