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?
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, the same size, and each pair of socks is connected 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?
4. One train leaves Los Angeles for new york at the speed of 15km per hour, and another train leaves new york for Los Angeles at the speed of 20km per hour. If a bird starts from two trains at a speed of 30 kilometers per hour, starts from Los Angeles, meets another train and returns, and flies back and forth in turn until the two trains meet, how long does the bird fly?
You have four jars containing pills, and 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?
6. 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?
7. Perform the following operations on a batch of lamps numbered 1 ~ 100, and turn them all on: turn the switch in the opposite direction every multiple 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.
8. Imagine yourself in front of a mirror. Excuse me, why can the image in the mirror be upside down, but not upside down?
9. A group of people held a dance, each 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?
10, 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?
17, 1 Yuan, one bottle of soda, two empty bottles for one bottle. Q: How many bottles of soda can you drink at most if you have 20 yuan money?