Seek some puzzles and answers, the more the better. Find something new.

1. There are two unevenly distributed incense, and the burning time is one hour. What method can you use to determine the time of 15 minutes?

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

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?

A: The ages of the three girls should be 2, 2 and 9. Because only one child has black hair, that is, only she has grown up, and the other two are still very young, that is, less than 3 years old, with light hair. The reorganization manager should be at least 25 years old.

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 my brother to return $5 to three guests. Unexpectedly, my brother was insatiable, and only returned 1 USD each, and secretly took it away by himself. But at the beginning, the three of them paid 30 dollars, so 1 dollar?

Answer: ***30 yuan includes 27 yuan (25 yuan gave it to the boss+younger brother embezzled 2 yuan) and everyone paid back 1 yuan (* * * 3 yuan). 2 yuan plus 27 is totally confusing.

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, 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?

Answer: every pair of socks is taken apart, and each person takes a pair, and there are no left and right socks. Finally, two pairs of black socks and two pairs of white socks were taken back.

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?

Answer: Convert the flight distance of birds into time calculation. Let the distance between LA and new york be a, the time when two trains meet is a/( 15+20)=a/25, and the flying speed of birds is 30, then the flying distance of birds is a/25*30=6/5a.

6. You have two cans, 50 red marbles and 50 blue marbles. You can place marbles in the way you imagine. After they are released, you can choose a jar at random and put a marble in the jar. How can we give red marbles the greatest chance of being selected? What is the exact probability of getting the red ball in your plan?

Answer: One jar contains a red ball, and the other jar contains 49 red balls and 50 blue balls. The probability is close to 75%.

This is the maximum probability that can be achieved.

In fact, just put a jar

Put the remaining balls in another jar, and the probability of taking out the red ball is greater than 50%.

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?

Answer: Take pill 1 from tank 1, pill 2 from tank 2, pill 3 from tank 3 and pill 4 from tank 4. According to 10 pills, the ratio is positive.

There is something wrong with the medicine in the jar as heavy as usual.

8. Xiaoming and Xiaohua bought 10 Jin of honey and put it in a big bottle. Divide the honey equally, there are only two empty bottles, one is exactly 7 kg and the other is exactly 3 kg. How can I separate honey in the simplest way? Remember to use the simplest method, which is the method with the least number of times.

Answer: 10 kg bottle, 7 kg bottle, 3 kg bottle.

10 0 before the start

1.3 7 0

2.3 4 3

3.6 4 0

4.6 1 3

5.9 1 0

6.9 0 1

7.2 7 1

8.2 5 3

9.5 5 0

One ***9 steps, this method is the least, and those who do 10 steps should think twice.

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.

Answer: when the square root of a number is an integer (that is, a complete square number), it faces down and the other faces are up.

So the numbers 1, 4, 9, 16, 25, 36, 49, 64, 8 1, 100 are facing down.

10, three hunters crossed the river with a black bear and two brown bears.

The boat is so small that it can only carry two people, or two bears, or one bear across the river at a time.

All three hunters can row a boat. Black bears are trained by hunters to row boats.

But once the number of bears exceeds the number of people, bears will eat people.

How can I cross the river safely?

Answer: The black bear took a brown bear across the river first, and then he rowed back to take another brown bear across the river. When the black bear rowed back, two tearful people crossed the river, a hunter brought a brown bear back, a hunter brought a brown bear across the river, two hunters rowed back and brought two brown bears across the river twice.

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?

There are three people wearing black hats. Suppose there are n people wearing black. When N= 1, the person wearing black will like to see everyone else is white.

Make yourself black. So when the lights are turned off for the first time, there should be a sound. It can be concluded that N> 1. For everyone who wears black, he thinks he is white when he sees the black hat of N- 1. But after waiting for N- 1 times and no one hits himself, every black person can know that he is black. So when the lights were turned off for the nth time, n people hit themselves.

12, there are 10 boxes of cans, and this 10 box contains 20 boxes, each box 1 kg.

But there is a box, and each box is only 9 taels.

There is only one scale now, and only one scale is allowed.

We must find out the box in question.

[Premise: You can't say lifting by hand, see which is lighter]

Answer: number the boxes as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

Take one case from 1, two cases from No.2 ... 10 and ten cases from No.0. * * * There are 55 boxes.

Put the box on the scale and look at the indicator. 10 cases are all 1 kg per case, the index of 55 cases should be 55 kg, and the title says there is a case of 9 Liang per case. Judging from the method of taking boxes just now, if it is 1 and 1, only one box is taken, then the index should be 55 kg. Fourth place ... 10, the index is 54.8, 54.7, 54.6, 54.5, 54.4, 54.3, 54.2, 54. 1 54. You can know which one is lighter by the final weight.

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: 39 bottles, starting from the second bottle, equivalent to 1 yuan to buy 2 bottles.

14. At the market, a peasant woman sells her eggs in a basket. A young man on a bicycle accidentally bumped into her basket, which turned over and broke the egg. The young man wanted to compensate her for the loss and asked, "How many eggs are there in the basket?" "I don't remember the exact number," the peasant woman replied, "but I know that when I take out eggs from the basket two at a time or three at a time, four at a time, five at a time, and six at a time, there will always be one left in the basket, but when I take out eggs seven at a time, there will be none left in the basket.

How many eggs are there in the basket?

Answer: 30 1. In this problem, we must first know that the least common multiple of 2, 3, 4, 5 and 6 is 60, so this number is 60x+ 1, and because this number can be divisible by 7, x=560x+ 1=30 1. Of course, you can say 72 1, but for the sake of reality.

15. A lady went shopping with two banknotes from 50 yuan and just bought something worth 100 yuan. She bought grapes from 22 yuan, apples 1 1 yuan, oranges, 30 yuan, peanuts 15 yuan, garlic 14 yuan, and washing powder, 8 yuan. But this old lady is a freak. She has five shops to buy things. I only hope that one of the shops can give me change, and I don't want to change it. Excuse me, is there such a just thing?

A: There are many answers. The old lady went to a store first, bought 1 1 yuan apple and 14 yuan garlic with two 50 yuan, and took back 39 yuan and 36 yuan (one 20 yuan, one 5 yuan and four coins) and (one 20, one 5 yuan and one sum 1).

Then I went to the second store and bought grapes with one 20 yuan and two coins (leaving one 20 yuan and two coins 10 yuan and two 5 yuan and three coins).

I went to the third store and bought an orange, a 20 yuan and a 10 yuan (one 10 yuan, two 5 yuan, and three coins left).

I went to the fourth store and bought a 10 peanut and a peanut from 5 yuan (one from 5 yuan had three coins left).

I bought washing powder in the fifth store with the last sum of money, 8 yuan (a 5 yuan with three coins left).

I only found the money at the first store and didn't change it. . Bought something in five stores,

16. Three frogs can eat three bugs in three minutes, so how many frogs can eat 81 bugs in 27 minutes?

A: Nine. Three frogs ate three bugs in three minutes, so they can eat twenty-seven bugs in twenty-seven minutes. Now they need to eat 81, so they can only multiply the number of frogs by three.

17. There are three boxes: red, green and yellow.

Only one box has a prize. There is a note on each box. Three notes contain three sentences, only one of which is true.

The red box says: The prize is not in the red box.

The green box says: The prize is not in the green box.

The yellow box says: The prize is not in the red box.

Which box is the prize in?

A: The red box, because only the red box has prizes.

18. 1 2 3 4 5 6 7 8 9= 100

You can only add and subtract to make these numbers finally equal to 100.

Because there are many answers.

So who can do this problem with the least symbols?

A:123+45-67+8-9 =100.

19. Xiaoming's son is my son's father, so my relationship with Xiaoming.

A: There are four possibilities. 1. Xiaoming's son and I are the same person. Then Xiaoming and I are father and son or mother and son.

I am not alone with Xiaoming's son. Then I am the wife of Xiaoming's son, and then Xiaoming and I are the mother-in-law relationship.

20. On a snowy night, you drive home. On the road, you see three people on the road. One is a seriously ill old man, the other is a doctor who saved your life, and the other is your dream lover. They all asked for a ride, but your car can only carry one person. What would you do?

The first thing to know is: 1. The old man is dying. You really want to repay this doctor. I missed this opportunity and don't know if I can meet it again next time. The person you love will go abroad soon, and there is no chance to express it again.

A: It is best for doctors to take the elderly to the hospital and accompany their loved ones. But everyone has their own choice, and this answer can only be said to be the most comprehensive answer, not necessarily the most suitable for you.