Transcription

1 !"#$%"$&"'()$ *+,,')- &"'+%."/ $ )8%"$9)2-"$: ;+/)$<=>< A man wanted to buy sunglasses at $60 He gave the shopkeeper a $100 note The shop had no change The shopkeeper changed the $100 at the neighbor s He got 10 notes of $10 each The shopkeeper gave the glasses to the customer He also gave him the change for $100: or $40 Later, neighbor comes to say $100 note was forged. The shopkeeper gave him a valid $100 How much did the shopkeeper lose? 2/ 46

2 &"'+%."/ The extra information is the exchange with the neighbor Since the shopkeeper got $100 and then gave it back, no loss was incurred. There was no effect on the solution. So most people would say he lost $100 = $40 in cash and $60 the watch Actually, he did not lose $60. He lost the cost of the watch. Solution: $40 and the cost of the watch, whatever that was. 3/ 46 CDE)$<F$J"/%23K.8%"2D$./@"243%."/ Three friends went into a restaurant to have a meal. Each paid $10 for his meal. As they were getting into their car, the owner of the restaurant saw them from a distance and told the cashier, These are my friends, go give them a $5 discount. The cashier took $5 from the cash box. Thinking that it would be difficult to divide the $5 into three equal parts, he gave each customer $1. They asked him to thank the owner and left. Since each had paid $9, the total paid was $27. The cashier stole $2, bringing the total to $29. Where is the missing $1? 4/ 46

3 &"'+%."/ The contradictory information is the adding of two different amounts The $2 in the pocket of the assistant cannot be added to the $27 It is already included in it The guys paid $27 broken down into $25 in the cash box and $2 in the assistant s pocket 5/ 46 CDE)$MF$0(".K$%H)$PB(."+-$&"'+%."/ &"'+%."/F$P/'D$"/8)Q$3@%)2$%H3%$.%$B)8"4)-$ ><A <L$!"#$43/D$8+B.8$4)%)2-$"@$-".'$K")-$3$ H"')$H3()$.@$.%$4)3-+2)-$<$R$S$R$M$4)%)2-O &"'+%."/F$3$H"')$K")-$/"%$H3()$-".'

4 CDE)$MF$0(".K$%H)$PB(."+-$&"'+%."/$$ I jog early in the morning. I have to get dressed in the dark so as not to wake my wife up. I pick up my stuff from the jogging drawer then I get dressed in the bath room. In the drawer, there are 10 red and 10 green socks. What is the minimum number of socks I have to draw so that I can be assured that there are at least two of the same color? 7/ 46 &"'+%."/ Everyone says 11 as if they want to ensure the husband will take at least 10 BUT if he takes 3, that would be enough With 3, here are the possible combinations 3 red 2 red and 1 green 1 red and 2 green 3 green In all cases, he has two of the same color. That is the minimum He cannot take 2 because he might get / 46

5 CDE)$TF$U"/V%$IW/"2)$PB(."+-$X38%- A poor beggar could not afford cigarettes. He went around collecting already smoked cigarette stubs. He would group 4 cigarette stubs to make one full cigarette and then smoke it. One day, he collected 16 stubs How many cigarettes can he smoke? 9/ 46 &"'+%."/ The obvious fact is that he can smoke 4 cigarettes BUT that leaves him with 4 stubs which make up one more cigarette Answer: 5 cigarettes 10 / 46

6 CDE)$NF$ A man leaves his office everyday at the same time. His wife drives from home to pick him up. She has it timed so that she arrives at his office just as he is leaving it. They turn around and head home. They get there at the same time every day. One day, he finished work 1 hour earlier than usual. He decided to walk along the road his wife uses to reach him. After a while, he saw her driving towards him. He flagged her down. They turned around and went back home. This time, they got home 30 minutes earlier than usual. How many minutes did he walk before he met his wife? 11 / 46 &"'+%."/ Most people start calculating from the man s point of view Express the question differently: How much time did he save his wife? The answer: 30 minutes Therefore, he met her when she was going to drive 30 more minutes: 15 to get to the office and 15 back Solution: he met her 15 minutes before she was supposed to meet him, therefore, he walked for 45 minutes 12 / 46

7 CDE)$NF$YRE2)--$%H)$Z+)-%."/$ An egg seller told his wife: I run out of eggs in the shop A buyer said : I want to buy! your eggs and! an egg. I sold him what he wanted. Another man came and said the same thing. I sold him what he wanted. A third man came along and asked for the same thing. I sold him what he wanted. I then ran out of eggs. How many eggs did the egg seller start with before the first buyer came? 13 / 46 &"'+%."/ The only way is to start backwards: The question: what should he have so he can sell all his eggs? One egg: half my eggs and half an egg Now it becomes easy to learn that each sale is odd so that we don t break any eggs The next sale was 3: half my eggs (1!) and! and egg with 1 remaining The next sale cannot be 5 as that leaves 2 (2! and!) So it had to be 7 (3! and! leaving 3 for the next sale) 14 / 46

8 A cat and dog ran a race. The cat and the dog had to run 100 feet, reach the end, turn around and go back to the starting point. The strange thing about this race is that the cat and the dog had to hop and not run. The dog ran in leaps of 3 feet each while the cat ran in leaps of 2 feet. Their speeds? For each 3 leaps of the cat, the dog leapt 2 at the same time. Did he or she win? &"'+%."/ The dog and cat have the same speed The dog leaps 2 times of 3 foot each The last leap will be at 99 feet so the dog will go over the 100 foot mark and then have to return The cat reaches 98 feet and hops to 100 and then returns The cat beats the dog Since the question was: does he or she win, most people would say: she wins because they think of the cat as a female and the dog as a male Solution: the cat wins. (Saying he or she is indeterminate) 16 / 46

9 ? Each square is the sum of the one above it and the one to its left Therefore, the answer is = 57 CDE)$]F$J23,D$*3%%)2/- CDE)$^F$_H3%$IX$&"'+%."/- An intelligent woman wanted to marry a most intelligent man. She had 3 very intelligent boyfriends. She sat the 3 men around a round table and blindfolded them. She told them she will place a red or a white hat on each head On removing the blindfolds, each man would be able see the other two hats but not his own. She said: if you see at least 1 red hat, you should raise your hand. I will marry the first man to correctly deduce the color of his hat She gave them all red hats. They all raised their hands. Moments, one man said, My hat is red. How did he find out? 18 / 46

10 &"'+%."/ A bit difficult but you have to imagine one of the men saying: Let us assume we have men A, B and C A asks: What if my hat were white? Since B and C are intelligent, assume the position of B. B would look at A and see he is white. He would look at C and see he is clapping. Therefore B would know C is clapping for him and would guess his color Since he did not, A concludes his color is not white but red This hesitation on the part of B and C proved that A was more intelligent 19 / 46 CDE)$>=F$0!0$3/K$`PCJ!0$*+,,')- Cut the cake into 8 equal pieces using only 3 straight cuts. There are 2 solutions to this puzzle. 20 / 46

11 &"'+%."/-$>$3/K$< Solution 1: cut the cake into 4 equal sectors (one straight cut and then another at 90 degrees to it). Then cut it horizontally to get 8 equal pieces Solution 2: do the same as Solution 1 to get 4 pieces. Then stack them on top of one another and cut them in two to get 8 pieces 21 / 46 CDE)$>=F$0!0$3/K$`PCJ!0$*+,,')-$ 3@%)2$#H.8H$D"+$#.''$-'3E$D"+2$@"2)H)3K I have a friend who can tell the score of every football match before it starts. He is always right. How can that be? What was the name of the Secretary General of the United Nations, in There is a solution! Mr. and Mrs. Nammour have a strange family. They have 5 children. Half of them are girls. How can that be? 22 / 46

12 The score of every match before it starts is 0 0 Everyone will say that in 1945 there was no UN so no solution. But the name of the Secretary General of the UN in 1945 was Ban Ki-moon. It was also his name in 1946, 47, etc. The Nammour family: half of the 5 children were girls. The other half was also girls. 23 / 46 &"'+%."/- CDE)$>=F$0!0$3/K$`PCJ!0$*+,,')- Why is the cover of a manhole (plaque de regard) Round when its frame is a Square? 24 / 46

13 &"'+%."/ A square cover has a side shorter than the diagonal of the surrounding square. It might fall into the hole. By making the cover round with a lip of 1 cm, it can never fall into the round hall 25 / 46 CH)$@"''"#./W$%DE)-$83/$"/'D$B)$ -"'()K$BD$a2+%)$X"28)Q$ *)2-.-%)/8) 3/K$Y'3B"23%."/A YR8)E%$@"2$%H)$4)8H3/.83'$ E+,,')-Q$3''$"@$%H)4$83/$B)$ -"'()K$BD$8"4E+%)2$E2"W234-

14 G)8H3/.83'$*+,,')- U)8.-."/$C2))$*+,,')- You have 12 marbles One of them is either heavier or lighter than the rest. In three weighs on a balance scale, you must determine which is the odd marble. How do you do this? 28 / 46

15 U)8.-."/$C2))-F$Y./-%)./V-$*+,,') In a street there are five houses, painted in 5 different colors. In each house lives a person of different nationality These 5 homeowners each drink a different kind of beverage, smoke different brand of cigar and keep a different pet. Use the clues on the next slide to find out who owns the fish! It is not certain that Einstein created this puzzle 29 / 46 Y./-%)./V-$*+,,')$ bu"+b%@+'$.%$#3-$h.4cl 1. The British man lives in a red house. 2. The Swede keeps dogs as pets. 3. The Danish man drinks tea. 4. The Green house is next to, and on the left of the White house. 5. The owner of the Green house drinks coffee. 6. The person who smokes Marlboro rears birds. 7. The owner of the Yellow house smokes Dunhill. 8. The man living in the center house drinks milk. 9. The Norwegian lives in the first house. 10. The man who smokes Winston lives next to he who keeps cats. 11. The man who keeps horses lives next to he who smokes Dunhill. 12. The man who smokes Kent drinks beer. 13. The German smokes Lucky Strike. 14. The Norwegian lives next to the blue house. 15. The man who smokes Winston has a neighbor who drinks water.

16 &"'+%."/ U)K+8%.()$7)3-"/./W$&"'+%."/-$ It happened one day that Miss Pink, Miss Green and Miss Violet met for lunch. It so happened that they were wearing jackets of three different colors: pink, green and violet. The lady wearing the violet jacket said: Isn t it strange that none of us is wearing the color that matches her name?. Miss Green replied: Yes, that is true. What was the color each lady was wearing? 32 / 46

17 0/"%H)2$U)K+8%.()$7)3-"/./W$ *+,,') The table shows the results of a particular tournament between three teams: A, B and C. Each team played a single match against the other two, so we had 3 matches. Find the score of every one of the 3 matches knowing that some results are missing from the table. 34 / 46

18 a2+%)$x"28)$*+,,')- *+,,')-$#.%H"+%$ *+,,')$

19 J"'+4B+-V-$*2"B')4F$ &%3/K$3/$YWW$"/$.%-$YKW) 37 / 46 &"'+%."/ Simply slam the egg softly on the table The shell will break The break will be good enough for stabilizing it No one said you could not break it! 38 / 46

20 X'.EE./W$%H)$J"./-$dE-.K)$U"#/ You have 200 coins laid up on a table There are 20 Tails and 180 Heads. You cover the table with a blanket Now put your hands under the blanket without seeing the coins. Task: split the coins into 2 groups that have the same number of Tails. 39 / 46 &"'+%."/ This is a great puzzle Move your hand under the blanket Take any 20 and flip them over That will leave you with the right combination Example: say the 20 that you selected had 8 Tails and 12 Heads That means the remain 180 will have 12 Tails and 168 Heads (because we only had 20 Tails) When you flip the newly found 20, you will get 12 Tail and 8 Heads There will be 12 Tails in the large group and 12 in the small group 40 / 46

21 CH)$U.-8"//)8%)K$\.WH%$a+'B I have 3 switches next to a door One for the entry, one for the corridor and one for the table lamp in my office Each lamp is connected to a cable coming to the switch box Only the cable of the Desk Lamp in the office is connected to its switch We do not know which switch it is connected to You can manipulate the switches the way you want : ONCE Then you can visit the office : ONCE Find a way to determine which switch turns it on/off. 41 / 46 &"'+%."/ Turn switch 1 on for 5 minutes Wait then turn it off Turn on switch 2 Now go to the room Touch the bulb to see if it is cold or warm If it is warm, then switch 1 is the link If it is on, then switch 2 is the link If it is cold and off, then it is switch 3 42 / 46

22 GD$&.-%)2V-$0W) My sister is a very elusive person (Especially about her age). Her doctor asked her how old she was. She said: In two years time, I will be twice as old as I was five years ago. How old was she when she said that? 43 / 46 &"'+%."/F$YRE2)--$%H)$Z+)-%."/$U.@@)2)/%'D In two years time, I will be twice as old as I was five years ago. Ask the question differently: the difference between in two years and five years ago is 7 years To be twice as old in five years, means she was 14 then OR 12 today Try it: in two years time I will be 14 and 5 years ago, I was 7 So in two years time (14) I will be 2 times what I was 5 years ago (7) 44 / 46

23 CH)$K.3W234$ -H"#-$D"+$%H)$ 8"'+4/$3/K$ 2"#$%"%3'-A X./K$%H)$ 4.--./W$%"%3' Extra Information: the different symbols You do not need them. Simply add the totals on the right: 4 x 110 = 440 Add the totals on the left: =320 So the missing total is = / 46

24 CH)$YRE3/K./W$_3%)2$\.''D A Water Lily floats on the surface of a circular pond. As it grows, it doubles its diameter each day. If it took the Lily 10 days to cover the whole pond s diameter, how long did it take to cover half the pond? 47 / 46 &"'+%."/ Avoid the Obvious Solution: 5 days Solution: on the last day, it doubled and filled the whole pond Therefore, on the previous day, it covered half of it (by diameter) 48 / 46

25 C#"$X3%H)2-$3/K$C#"$&"/- Two Fathers and Two Sons were walking on a country road They found 3 coins of $1 each They distributed the coins equally without anyone getting a lower share How could they do that? 49 / 46 &"'+%."/ Don t ignore the obvious facts Obvious fact: a father can also be a son We had a grandfather, a father and a son The father was a son and a father, therefore, we had 4 personalities 50 / 46

26 X./K$%H)$5)R%$5+4B)2$./$%H.-$&)2.) ? 51 / 46 &"'+%."/ Crazy pattern Don t look for arithmetic. This is what they expect you to. Each number describes the pervious one (except the first) So 11 means: in the previous line there is 1 One And 21 means: in the previous line there are 2 One s And 1211 means: in the previous line there is 1 Two and 2 One s And means: in the previous line there is 1 One, 1 Two, 2 One s So our solution is work it out 52 / 46

27 G"()$P/)$`'3--$P/'D$A$A$A$A In the top row, you start with 3 empty glasses to the left of three glasses filled with orange juice. Can you move only one glass and end up with the pattern shown in the lower row? 53 / 46 &"'+%."/$ I didn t know you could pour orange out of the cup Simply pour the content of Cup 2 (from the left) into Cup 2 from the right to get the solution 54 / 46

28 CH)$*"E+'3%."/$J"/%2"'$*2"B')4 A government was worried about the high rate of population growth in its country. It issued this decree to help control overpopulation. Ignore what children a family already had. Use these rules: 1) Families can go on having children until they get a son. They must then stop having any children. 2) They cannot have more than 3 girls. They must also stop. 3) Families can stop any time after 1 child or 2 children What happens to the population balance after many years? 55 / 46 &"'+%."/F$0-1$%H)$7.WH%$Z+)-%."/ Everyone gets this wrong Everyone goes on arguing The question is: what is the probability of getting a male in each birth? The answer is 50% Therefore, no matter what the government does, each lady going to deliver will deliver according to this natural law There is no overall change in gender distribution BUT there is a change in the distribution of family size That was not the question!! 56 / 46

29 CH)$X3%3'$U2)34$./$%H)$J./)43 A man and his wife went to the cinema. They were watching a boring film, so he slept in his seat. He dreamt about the film and saw himself being executed instead of the criminals in the story. His wife noticed that he was sleeping, so to wake him up, she jokingly tapped the back of his neck with a chocolate bar. In his dream, he saw the executioner s sword fall right on his neck. The shock gave him a heart attack and he died without uttering a sound. Is there anything wrong with this story? 57 / 46 &"'+%."/F$J"/%23K.8%"2D$I/@"243%."/ How could we tell what he dreamt if he died in his sleep? 58 / 46

30 _H3%$.-$%H)$G.--./W$&D4B"'O &"'+%."/F$J23,D$*3%%)2/ Follow the blue squares. IT should give you a hint Each blue square is followed by a green rhombus except the first Each green rhombus is followed by 4 yellow diamonds except the first two Each 4 yellow diamonds icon is followed by the purple icon except the first 3 Solution: first we put a blue squiare Then we put a blue square followed by a green rhombus Then we put a blue square, a green rhombus followed by 4 one yellow diamonds icon, and so on 60 / 46

31 !"#$G3/D$C"+2/34)/%-O If 36 players are to play in a tennis tournament, you can easily find out how many matches are required by drawing the tournament tree and counting the matches. But there is a simpler and more elegant way of find the answer, AND without pencil and paper. How can you do it? And for any number of players too? 61 / 46 &"'+%."/F$0!0 There is no need to go to great thinking There is no need to find mathematical solutions If you have X players, you need X-1 matches to eliminate all but the winner So if we have 36 players, we need 35 matches If we have 233 players, we need 232 matches 62 / 46

32 1./K$3%%)/%."/