1. Burn an uneven rope , From head to tail, all in all 1 Hours . There are now several ropes of the same material , How to use the method of burning rope to count an hour and 15 minutes ?
answer 1) Three ropes , First ignition ends , Second ignition end , The third one doesn't point to the first rope and burns （30 minute ） after , Ignite the other end of the second rope , The second rope is burned （45 minute ） after , Ignite the third rope at both ends , Third rope burning
finish （1 hour 15 branch ） after , Time complete
2. You have a bucket of jelly , There is yellow , green , Three kinds of red , Close your eyes and grab two of the same color . Grab as many as you can make sure you have two jelly of the same color ?
answer 2） According to the drawer principle ,4 individual
3. If you have infinite water , One 3 The lift of the litre , One 5 The lift of the litre , The shape of both pokes is uneven , Ask how you can accurately weigh it 4 Liter of water ?
answer 3）3 Full ;3 rise -〉5 rise （ Full injection ）;3 Full ;3 rise -〉 rise （ Remnant 1 rise ）;5 Up and down ; rise -〉5 rise （ injection 1 rise ）;3 Full ;3 rise -〉5 rise
; complete （ another ： Programming solution by backtracking method ）
4. A fork in the road leads to the honest and the lying . Two people here , One known to be honest , The other is a liar . The honest country always tells the truth , A liar always lies . Now you're going to lie , But I don't know which way to go , You need to ask these two people . What should I ask ?
answer 4） Ask one of them ： And another person would say which road is to the honest country ? The way the answer points to must be to the liar state
5.12 A ball, a balance , Now I know that only one is different from other weights , Ask how to weigh it, and find that ball three times . What about one ?（ Note that this question does not mean that the weight of that ball is light or heavy , So it needs to be considered carefully ）
answer 5）12 Balls ： for the first time ：4,4 If it's flat ： So take the rest of the ball 3 Put it on the left , take 3 A good ball on the right , call ： If the left side is heavy , So take two balls and weigh them , Which weight is the inferior product , The third thing is Ping , It's a bad product , If it is light, it is the same It's flat , So there's one defect left , It can also be said that the inferior products are lighter or heavier than the genuine ones according to the needs . If it is not ： So, it's okay Set left heavy right light , For easy explanation , To the left 4 A ball called a heavy ball , right 4 A light ball , be left over 4 A good ball to take a heavy ball 2 Seed , Light ball 2 The one is on the left ,
Right side 3 A good ball and a light ball . If the left side is heavy , Weigh the two heavy balls , A heavy inferior product , If you are flat, the right light ball is defective . If the right weight , Weigh the two light balls on the left , A light inferior . as
Guoping , Weigh the remaining two heavy balls , A heavy inferior product , If you are flat, you can leave the light ball defective .13 Balls ： for the first time ：4,4, If it's flat Remnant 5 The ball can still find the defective products by the way above , It's just not known
The inferior is heavy or light , If it is not , ditto
6. In one day 24 In the hour , Clock's clock , There are several times when the minute and second hand are completely coincident ? What time is it ? How do you figure it out ?
answer 6）23 second , Because the needle is going to turn 24 circle , Only when the clock is turned 1 circle , And the interval between the minute and the clockwise coincidence is obvious >1 hour , They have 23 Secondary coincidence opportunity , There is a coincidence opportunity for the second hand in each Reclosing , So it was 23 The time of sub coincidence can be calculated by comparing with the watch , Also can be obtained by the equation
7. Known ： There is only one tank per aircraft , Planes can refuel each other （ Attention is mutual , No gas dispenser ） A tank of oil
It can be used for a plane to fly half a circle around the earth , problem ： To return at least one aircraft around the earth to the airport at the time of departure , At least a few planes need to be deployed ?（ All aircraft take off from the same airport , And it has to be safely returned to the airport , No midway landing allowed , There is no airport in the middle ）
answer 7)3 Aircraft 5 Sorties , Flying method ：ABC 3 Take off at the same time ,1/8 place ,C to AB fill the tank up ,C Return ,1/4 place ,B to A fill the tank up ,B Return ,A arrive 1/2 place ,C Take off from the airport to the other direction ,3/4 place ,C Same as that of the empty tank A Share the remaining oil equally , meanwhile B Take off from Airport ,AC reach 7/8 Same B Share the remaining oil equally , just 3 Aircraft return at the same time .
So it was 3 Aircraft 5 Sorties .
Two prisoners are in a cell . Every day, the prison provides a jar of soup for the cell , Let the two prisoners divide themselves . at first , These two people often have disputes , Because they always think that each other has more soup than they do . And then they found a way to make it both beautiful ： One person to divide soup , Let another person choose first . So the dispute was settled . however , Now a new prisoner is added to this cell , Now it's three people who can share soup . A new way to maintain peace between them must be found . What should I do ?
Press ： Psychological problems , It's not a logical problem
It's a soup , After the division, Party B and C will pick their own soup in any order , The remaining bowl is for a . So the sum of B and C must be the biggest they can get . Then mix the soup of the two of them and divide the soup again in the way of the two .
9 On a rectangular table n
A round coin of the same size . Some of these coins may not be entirely on the table , There may also be some overlap ; When you put another coin and its center is on the table , The new coins must overlap with some of the original ones . Please prove that the entire desktop can be used
4n Coins covered completely .
answer 9) To keep the new coin from overlapping the original one , The center distance of two coins must be greater than the diameter . in other words , For any point on the desktop , The distance to the nearest center of the circle is less than 2, therefore , The entire desktop is available n
Radius is 2 The coin cover of .
Double the scale of the table and coins , that , long , Small desktop with width of half of the original desktop , It can be used n Radius is 1 The coin cover of . that , Divide the original table into equal 4
A small table , So every small table can be used n Radius is 1 The coin cover of , therefore , The entire desktop is ready to use 4n Radius is 1 The coin cover of .
10 There are five houses in a row All houses have different exterior colors All the owners come from different countries All homeowners have different pets ; Drink different drinks ; Smoking different cigarettes Tips ：
The British live in red houses
The Swedes have a dog
The green house is on the left side of the White House
The owner of the green house drinks coffee
Smoke pall mall The owner of the cigarette raises birds
Yellow house master dunhill
The owner in the middle drinks milk
Norwegians live in the first house
Smoke blend The people live next door to the cat house
The owner of the horse house is pumping dunhill Next door to the family
Smoke blue master The owner of the house drinks beer
German pumping prince
Norwegians live next to the blue house
People who drink only boiled water live in pumping blend Next door to
ask ： Who feeds fish ?